Lets begin by looking into a simple example of an application accepting two command line arguments name (-name) and message (-msg). name is required argument and msg is optional argument with default value “Good Morning”. If msg is not passed, it will take the default value.
The code above illustrates about defining command line argument object. First thing define a command line argument (ex. HelloWorldCmdLineParams) class from ChoCommandLineArgObject, it indicates that this object is a command line argument object. And it must be decorated with ChoCommandLineArgObjectAttribute to complete the definition. In this example, we specify the name of application and copyright message. These values are used by parser to display the formatted message on the console window. If these options are not specified, AssemblyTitle and AssemblyCopyright of the entry assembly will be defaulted to these members respectively.
It is very simple and clear way of specifying command line options using attributes.
Listed below are test runs of the programs with different set of arguments and its output.
So far we have seen some of the samples of using Command line arguments in the executable. Try with some other combinations by yourself to test it out.
It is an argument defined to accept value from command line arguments from a specified position. Position starts with value 1. A command line object member decorated with ChoPositionalCommandLineArgAttribute will be called positional argument.
After executing the program with the above command line argument, the above object members PosArg1 and PosArg2 will be loaded with APos1 and APos2 values. Please note, the positional argument values are mixed up with Switch Named command line arguments. When it comes to parse and load the positional arguments, parser identifies position arguments in the order from left to right starting with position 1 and loads them.
It is an argument defined to accept value from command line arguments for a specified command line switch. A command line object member decorated with ChoCommandLineArgAttribute will be called switch named command line argument.
After executing the program with the above command line argument, the above object members Name and Message will be loaded with ‘Raj’ and ‘Hello World’ values.
This attribute is applied to the class which will recieve and loaded with command line arguments, ie. the class defining all the command line arguments available to the program. This object will reveive the values specified in the command line arguments to the executable.
This attribute is applied to the command line argument class in order to provide very detailed descriptive help text to the them. You may specify them multiple times to the class. These text are displayed at the end of Usage Text seperated by newline.
This attribute can be applied to the fields and properties of class to designate as switch named command line arguments. This attribute designate the members of the class receive the command line argument value for the specified switch.
There are three descriptive parameters in this attribute.
Providing default value for a command line argument will allow the parser assign this default value to the member when the parameter is not specified at the command line to the executable. Note that setting this parameter does not prevent the user from specifying a different value on the command line, it merely provides the default value should the user opt not to provide one.
In case the command line argument is passed for the concerned option and failed convert and assign to the member, fallback value is assigned to the member.
These parameters are optional to be used to formatting and make it to display elegant usage text. Below are the available parameters for use to format the usage text
This attribute can be applied to the fields and properties of class to designate as positional command line arguments. This attribute designate the members of the class receive the command line argument value for the specified position. Position always starts with 1.
There are three descriptive parameters in this attribute.
Besides above descriptive properties, you can specify fallback value, default value, formatting parameters to this argument. Alias can’t specified to this argument.
Command Line Argument parser supports all members defined with any CLR datatype. No restriction at all. All the built-in datatypes are automatically managed by parser, no special handling of conversion is required. Below are the supported built-in types are
If there is an exception occurs during the parser conversion and assignment of the the command line value to a member, it will throw ChoCommandLineArgException.
This section illustrates about special way of passing and handling bool values from command line arguments. Most of the command line values can be passed to the executable in the below switch:value format
This section illustrates how bool values are set without passing values explicitly. Parser looks for switch presents in the command line arguments for bool parameters. If the bool switch specified (/r), parser takes them as True value. If the bool switch specified as (/r-), parser takes them as False value.
6.2 Handling of complex datatype members
This section illustrates how to handle complex UDT data type members. There are number of ways to recieve, parse and assign the values to command line argument members.
- Callback Machanism
- ValueConverter Mechanism
6.2.1 Callback Machanism
This is easiest way to receive, parse and load the command line argument value to a member. This gives you ultimate control over handling any type of command line argument values in your object. Override OnBeforeCommandLineArgLoaded method in the command line argument object, which will be invoked for each command argument switch by the parser. There you write custom logic for the concerned member and load the member with value. Once you handle the situation, simply return True to tell the parser that you handled the conversion.
Listing 6.4 CommandLineArgObject with Callback override
[ChoCommandLineArgObject(ApplicationName = "Hello world", Copyright = "Copyright 2014 Cinchoo Inc.")]
public class HelloWorldCmdLineParams : ChoCommandLineArgObject
{
[ChoCommandLineArg("name", Aliases="n", IsRequired = true, Description = "Name of the person.")]
public string Name;
[ChoCommandLineArg("msg", DefaultValue = "Good Morning", Description = "Greeting message")]
public string Message
{
get;
set;
}
[ChoCommandLineArg("s", ShortName = "<int | INFINITE>", Description = "Sleep period.")]
public int Sleep
{
get;
set;
}
protected override bool OnBeforeCommandLineArgLoaded(string memberName, ref string value, object defaultValue, object fallbackValue)
{
if (memberName == "Sleep")
{
if (value == null)
Sleep = 0;
else
{
if (String.Compare(value.ToString(), "INFINITE", true) == 0)
Sleep = -1;
else
{
int timeout = 0;
int.TryParse(value.ToString(), out timeout);
Sleep = timeout;
}
}
return true;
}
else
return base.OnBeforeCommandLineArgLoaded(memberName, ref value, defaultValue, fallbackValue);
}
}
In the sample above, Sleep parameter is int type. But it gives option to take either int or INFINITE value as command line argument. In the callback machanism, we handle it by overriding OnBeforeCommandLineArgLoaded method.
Listing 6.5 Test1.exe with Sleep value passed
>Test1.exe /name:"Raj" /msg:"Hello world" /s:INFINITE
Hello world [Version 1.0.0.0]
Copyright 2014 Cinchoo Inc.
-- ConsoleApplication2.HelloWorldCmdLineParams State --
Message: Hello world
Sleep: -1
Name: Raj
6.2.2 ValueConverter Machanism
This is alternative way to receive, parse and load the command line argument value to a member. This gives you opportunity to perform conversion using ValueConverters. Either you can use existing converters or create new one and use them. In here I’ll show you to how create a new converter and use them in command line argument members. This approach lets you to reuse the conversion logic in a pluggable architecture.
First, lets define a ChoTimeoutConverter. It converts input string value to Timeout (int) value. You can define the converter class derived from either System.Windows.Data.IValueConverter (PresentationFramework.dll) or Cinchoo.Core.IChoValueConverter (Cinchoo.Core.dll). Both interfaces have the same methods. You can use whatever interface suited for your needs.
Listing 6.6 ChoTimeoutConverter class
public class ChoTimeoutConverter : IChoValueConverter
{
public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
if (value == null)
return 0;
int timeout = 0;
if (String.Compare("INFINITE", value.ToString(), true) == 0)
return -1;
else if (int.TryParse(value.ToString(), out timeout))
return timeout;
else
return 0;
}
public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
return value != null ? value.ToString() : String.Empty;
}
}
In above, defined ChoTimeoutConverter from IChoValueConverter interface. Implemented the methods. It is self-explanatory.
Now I’ll illustrate how to use the above converter in the command line argument member. Couple of ways you can use them in command line argument object.
- Defining Converter Attribute and use it
- Using ChoTypeConverterAttribute directly
6.2.2.1 Defining Converter Attribute and use it
This approach will let you define converter attribute for each converter. In the sample below shows you to define ChoTimeoutConverterAttribute for ChoTimeoutConverter class. The converter attribute must be drived from ChoTypeConverterAttribute class and pass converter type to its converter. See below example
Listing 6.7 ChoTimeoutConverterAttribute class
[AttributeUsage(AttributeTargets.Property | AttributeTargets.Field | AttributeTargets.Class, AllowMultiple = true, Inherited = false)]
public class ChoTimeoutConverterAttribute : ChoTypeConverterAttribute
{
public ChoTimeoutConverterAttribute()
: base(typeof(ChoTimeoutConverter1))
{
}
}
Once you have attribute defined as above, it can be used against command line argument member to perform conversion of the argument value as below
Listing 6.8 Using ChoTimeoutConverterAttribute in a member
[ChoCommandLineArgObject(ApplicationName = "Hello world", Copyright = "Copyright 2014 Cinchoo Inc.")]
public class HelloWorldCmdLineParams : ChoCommandLineArgObject
{
[ChoCommandLineArg("name", Aliases="n", IsRequired = true, Description = "Name of the person.")]
public string Name;
[ChoCommandLineArg("msg", DefaultValue = "Good Morning", Description = "Greeting message")]
public string Message
{
get;
set;
}
[ChoCommandLineArg("t", ShortName = "<int | INFINITE>", Description = "Timeout period.")]
[ChoTimeoutConverter]
public int Timeout
{
get;
set;
}
}
6.2.2.2 Using ChoTypeConverterAttribute
This illustrates how to use the converter class (ChoTimeoutConverter) directly to the command line object member without defining converter attribute for each converter class. Cinchoo framework provides common attribute class for this purpose. It is ChoTypeConverterAttribute. Simply use this attribute and pass the ChoTimeoutConverter type to its constructor as below.
Listing 6.9 Using ChoTypeConverterAttribute in a member
[ChoCommandLineArgObject(ApplicationName = "Hello world", Copyright = "Copyright 2014 Cinchoo Inc.")]
public class HelloWorldCmdLineParams : ChoCommandLineArgObject
{
[ChoCommandLineArg("name", Aliases="n", IsRequired = true, Description = "Name of the person.")]
public string Name;
[ChoCommandLineArg("msg", DefaultValue = "Good Morning", Description = "Greeting message")]
public string Message
{
get;
set;
}
[ChoCommandLineArg("t", ShortName = "<int | INFINITE>", Description = "Timeout period.")]
[ChoTypeConverter(typeof(ChoTimeoutConverter))]
public int Timeout
{
get;
set;
}
}
So far you have learned how to parse, convert and load command line argument value to its members using various methodologies.
6.3 Special handling of Enum
This section illustrates about special way of passing and handling enum values from command line arguments. Most of the command line values can be passed to the executable in the below switch:value format
Listing 6.10 Test1.exe with switch and values
>Test1.exe /name:"Raj" /msg:"Hello world"
Lets begin by defining enum type and command line argument object with enum member as below
public enum Action { ADD, DEL, UPDATE };
[ChoCommandLineArgObject]
public class COMPUTERCmdLineArgObject : ChoCommandLineArgObject
{
[ChoPositionalCommandLineArg(1, "\\\\computername", IsRequired = true, Order = 0)]
public string ComputerName;
[ChoCommandLineArg("action", IsRequired = true)]
public Action ActionValue;
}
Above code illustrates that Action enum is defined. It is consumed by COMPUTERCmdLineArgObject class by declaring ActionValue member. It must be declared with ChoCommandLineArgAttribute. All enum types must be decorated with ChoCommandLineArgAttribute.
Below is the test run shows how to pass enum value as command line argument
Listing 6.11 Test1.exe with enum value (Implicit way)
>Test1.exe "\\NYCDR1234234" /UPDATE
It illustrates that the enum values may be passed in /[EnumValue] format.
Listing 6.12 Test1.exe with enum value (Explicit way)
>Test1.exe "\\NYCDR1234234" /action:UPDATE
It illustrates that the enum values may be passed in /Switch:EnumValue format.
7. Customizations
There are ways to customize the parser, like command line switch characters, assignment seperators, usage switches, case sensitive handling of switches etc. The default settings should be good enough for most applications, but they are there for your customizations if you need to.
7.1 Specifying switch characters
This is special character used to prefix with swtiches when you pass command line arguments to the executable. Parser comes with default switch characters ‘/’, ‘-‘. It means that these are the available characters can be prefixed with switches. It can be customizable by opening [appExe].config or App.config file, add or edit custom configuration section ‘commandLineParserSettings’ to it.
Listing 7.1 CommandLineParserSettings config section
<?xml version="1.0" encoding="utf-8" ?>
<configuration>
<configSections>
<section name="commandLineParserSettings" type="Cinchoo.Core.Shell.ChoCommandLineParserSettings, Cinchoo.Core" />
</configSections>
<commandLineParserSettings switchChars="/, -" valueSeperators = ":, =" />
</configuration>
Cinchoo.Core.Shell.ChoCommandLineParserSettings is the configuration section object. Below are the available parameters for you to customize the parser
- switchChars – Optional. List of possible command line switch charactors can be specified here. Multiple characters acceptable. Must specify one character. Characters are separated by comma. Default values: “/, -“.
- valueSeparators – Optional. Specify list of possible switch-value separator characters. Multiple characters can be specified. Must specify atleast one character. Characters are separated by comma. Default values: “:. =”.
- usageSwitches – Optional. This is the switch used to display usage text. Specify list of possible usage switch strings. Multiple values can be specified. Must specify atleast one value. Strings are separated by comma. Default values: “?, h, help”.
- fileArgSwitches – Optional. This switch used to specify the file path containing command line arguments. Some programs may have long list of arguments. In order to avoid repeat passing the command line argument values to the executable, you can save them to a file and input the file using this switch. Multiple values can be specified. Must have atleast one value. Characters are seperated by comma. Default values: ‘@’.
- ignoreCase – Optional. True, command line switches are case insensitive. Otherwise false. Default value: True.
- showUsageIfEmpty – Optional. True, will show detailed usage text. Otherwise false. Default value: True.
- doNotShowHeader – Optional. True, will show header information like AssemblyTitle, Version, and Description. Otherwise false. Default value: True.
7.2 Case sensitive of Command Line Switches
You have a option to specify whether the command line switches are case sensitive or not, through ignoreCase parameter in ChoCommandLineParserSettings. Default is that switches are NOT case sensitive.
8. CommandLineObject Overrides
This section illustrates some of the important methods which can be overrideable in order to customize the parser.
8.1 GetUsage() Method
In general, the parser does the quite job of creating the usage text for you in most cases. In rare situation, you may want to customize the way you want the usage text would be. In this case, you can override GetUsage() method. It is a public method, return string value.
8.2 OnBeforeCommandLineArgLoaded Method
This method gets called before each command line argument value is loaded. In this method you have opportunity to validate the command line value, perform conversion or even replace with new value etc. Return true, instruct parser to stop processing of the value. Otherwise continue the process of loading the value.
8.3 OnAfterCommandLineArgLoaded Method
This method gets called for each command line argument is loaded. In here you have option to perform any post assignment tasks like dependent property values can be derived from this property.
8.4 OnCommandLineArgLoadError Method
This method gets called when there is an exception occurs when loading command line argument to a member. In here, you can perform exception handling. Return true, instruct the parser that you handled the exception. Otherwise false.
8.5 OnBeforeCommandLineArgObjectLoaded Method
This method gets called before the command line argument object is loaded. In this method you have opportunity to lookup the payload of the command line arguments overall, perform some pre validation or even replace the values with new ones etc. Return true, instruct parser to stop the parsing. Otherwise continue the process of loading the object.
8.6 OnAfterCommandLineArgLoaded Method
This method gets called after command line argument object is loaded. In here you have option to perform any post assignment tasks like dependent property values can be derived, validation etc.
8.7 OnCommandLineArgObjectLoadError Method
This method gets called when there is an exception occurs when parsing and loading whole command line argument object. In here, you can perform exception handling. Return true, instruct the parser that you handled the exception. Otherwise false.
8.8 OnCommandLineArgNotFound Method
This method gets called when no command line argument found in the argument list to the executable.
9. Advanced Topics
In this topic, I’m going to talk about some of the key advanced topics to understand and use in your projects when you use this parser. It helps you how effective the parser can be utilized in your projects.
9.1 Specifying Argument with Whitespaces
Most of the cases, the command line argument value without any whitespaces can be specified as it is. In case where the value contains white spaces, it must be surrounded by double quotes. For example,
Listing 9.1 Test1.exe with value contains white spaces
>Test1.exe /name:"Raj Nagalngam" /msg:"Hello world" /r:True
9.2 Specifying Quotation Marks into the value
By default double quotes (“) are the only recognized quotation marks. Inside the quotes you may escape quote character itself to insert a literal quotation mark into the value. It can be inserted as below (escaped using additional double quotes)
Listing 9.2 Test1.exe with value contains double quotes
>Test1.exe /name:"Raj""s msg" /msg:"Hello world" /r:True
9.3 Loading arguments from external file
A program may have multiple large, complex sets of command line arguments and wanted to run them multiple times, in this case you can save the values to external file and pass the file to the program. It saves time and effort of retyping the command line argument values for each run.
Listing 9.2 Test1.exe with value contains double quotes
>Test1.exe @"C:\Sample\CmdLineArgs.txt"
10. Validation
In this section, I’ll talk about how to validate each command line argument member values, different approaches of validation methods, etc. Any application that accepts input from command line arguments must ensure that the information is valid in terms of some set of rules that you specify. For example, you may need to check that a customer’s phone number has the correct number of digits, or that a date falls within a particular range. In addition, if the validation fails, you may need to send an error message that explains what is wrong.
Cinchoo provides library of classes, called validators, that supplies the code for validating command line argument members. For example, one validator checks for null strings and another validator checks that a string contains only specific set of characters etc. In some cases, you may want to define your own custom validator and use them to validate the member values.
There are special validaters used to compose, aggregate other validators and group them together in a rule set.
- ChoAndCompositeValidator – It groups other validators, all validators in this composite validator must be true for a successful validation.
- ChoOrCompositeValidator – It groups other validators, at least one validators in the composite validator must be true for a successful validation.
If you want to avoid validations using this library feature and take control of validation, you can do so in couple of ways
- Callback mechanism – OnAfterCommandLineArgLoaded override method can be used to put custom logic to validate the command line argument value.
- Property Setter mechanism – This is another place where you can do custom validation on these member values.
10.1 Using Validators
The following procedures explains how to use validators in your command line argument object members. There are two ways to use validators for your command line argument members
- ChoValidatorAttribute – An generic validator attribute, used in case specific validator does not have corresponding attribute.
- Validator specific attribute – These are customized validator attributes for each validator. For example, ChoStringValidatorAttribute is the attribute for ChoStringValidator class.
Cinchoo supports the following validators out of the box
- ChoValidators – Validators that Cinchoo library provides itself. You may find number of them under Cinchoo.Core namespace. For example, ChoNotNullValidator, ChoNotNullOrEmptyValidator etc.
- BCL Configuration Validators – Validators that .NET BCL library provides. You can find them System.Configuration namespace. For example, StringValidator, IntegerValidator etc.
- BCL DataAnnotation Validators – Another set of validators that .NET BCL library provides under System.ComponentModel.DataAnnotations namespace.
10.1.1 Using ChoValidatorAttribute
This is one way of specifying validation rules to command line argument members. In case where there is no validator attribute available for a specific validator, this attribute is here to rescue. This attribute takes validator type as input. The validator type can be one of below derived classes
- Cinchoo.Core.ChoValidator – There are number of validators that Cinchoo framework library offers to use in your application.
- System.Configuration.ConfigurationValidatorBase (System.Configuration.dll) – These set of validators .NET BCL offers to use.
Below are the available optional properties for this attribute
- ConstructorArgs – Optional. Most of the validators accepts some mandorary parameters through constructor to perform the validation on command line object members. These parameters can be specified through this property. It takes object[] as value. These values are positional constructor arguments.
- ConstructorArgsText – Optional string value. The constructor arguments can be specified as text and each value is seperated by ‘;’.
- KeyValuePropertiesText – Optional string value. It is a key value pair seperated by ‘;’ character to set validator property values. For example, “MinValue=1;MaxValue=10”.
Listing 10.1 CommandLine Argument Object with validators
[ChoCommandLineArgObject(Description = "Utility to generate schema or class files from given source.")]
public sealed class ChoAppCmdLineParams : ChoCommandLineArgObject
{
[ChoPositionalCommandLineArg(1, "xmlfile", IsRequired = true, Description = "Name of an xml file to infer xsd schema from.")]
[ChoValidator(typeof(ChoNotNullOrWhiteSpaceValidator))]
[ChoValidator(typeof(StringValidator), ConstructorArgsText = "10")]
public string XmlFilePath
{
get;
set;
}
[ChoCommandLineArg("o", Description = "The output directory to create files in. The default is the current directory.")]
[ChoStringValidator(MinLength = 10)]
[ChoContainsCharactersValidator("A")]
public string OutputDirectory
{
get;
set;
}
}
In the sample above, the member ‘XmlFilePath’ is specified with 2 validations. It must be not null and must contain minimum 10 characters. The sample shows how you can use ChoValidatorAttribute to define the validators those dont have corresponding custom validator attributes. Note, multiple validators specified at the top level are combined and validated as AND condition by default. Validation orders are NOT guaranteed sequencial.
‘OutputDirectory’ member is decorated with custom validator attributes correponding to validators. In here, it is decorated with ChoStringValidatorAttribute and ChoContainsCharatersValidatorAttribute. It gives flexibilty, simplicity and type safety in declaring validators.
Create a console application and create an object of ChoAppCmdLineParams as below
Listing 10.2 Main method
class Program
{
static void Main(string[] args)
{
ChoAppCmdLineParams cmdLineParams = new ChoAppCmdLineParams();
Console.WriteLine(cmdLineParams.ToString());
}
}
Listed below are test runs of the program with different arguments
Listing 10.3 Test1.exe with no arguments
>Test1.exe
ConsoleApplication2 [Version 1.0.0.0]
Copyright c 2014
Utility to generate schema or class files from given source.
Found exception while loading `xmlfile` command line argument.
The string must be at least 10 characters long.
ConsoleApplication2.exe xmlfile [/o:<string>]
xmlfile Name of an xml file to infer xsd schema from.
/o The output directory to create files in. The default is the
current directory.
Press any key to continue . . .
In the above run, the executable was run without passing any command line arguments. The application is trying to instantiate the ChoAppCmdLineParams object. While creating such object, the framework tries to validate the member values. In this case, the positional command line argument ‘xmlFilePath’ is failed to validate. The application termintes with exception.
Listing 10.4 Test1.exe with incorrect output directory value
>Test1.exe "C:\Windows\Systems\cpanal.xml" /o:"C:\Windows\Systems\Xcpanal.xml"
ConsoleApplication2 [Version 1.0.0.0]
Copyright c 2014
Utility to generate schema or class files from given source.
Found exception while loading `o` command line argument.
The value must contains ALL of the 'A' characters.
ConsoleApplication2.exe xmlfile [/o:<string>]
xmlfile Name of an xml file to infer xsd schema from.
/o The output directory to create files in. The default is the
current directory.
Press any key to continue . . .
In the above test run, the executable was run with arguments. The positional argument ‘XmlFilePath’ passed the validation (not null AND contains more than 10 characters). But it failed at validating ‘OutputDirectory’. It does not contain character ‘A’ in it. The application terminates with exception.
Listing 10.5 Test1.exe with correct values
>Test1.exe "C:\Windows\Systems\cpanal.xml" /o:"C:\Windows\Systems\Acpanal.xml"
ConsoleApplication2 [Version 1.0.0.0]
Copyright c 2014
Utility to generate schema or class files from given source.
-- ConsoleApplication2.ChoAppCmdLineParams1 State --
XmlFilePath: C:\Windows\Systems\cpanal.xml
OutputDirectory: C:\Windows\Systems\Acpanal.xml
Press any key to continue . . .
In the above test run, the executable was run with valid arguments. The positional argument ‘XmlFilePath’ as well as ‘OutputDirectory’ passed the validation without any errors.
10.1.2 Using Custom Validator Attributes
Previous section I’ve talked about using generic validator attribute in defining validations on command line argument members. It paves the way to use the validators without validator attributes. Some validators comes with custom validator attributes. It is simple and straight forward to use and type safe. In the sample below, OutoutDirectory member defines 2 validators with its custom attributes.
Listing 10.6 CommandLine Argument Object with validators
[ChoCommandLineArgObject(Description = "Utility to generate schema or class files from given source.")]
public sealed class ChoAppCmdLineParams : ChoCommandLineArgObject
{
[ChoPositionalCommandLineArg(1, "xmlfile", IsRequired = true, Description = "Name of an xml file to infer xsd schema from.")]
[ChoValidator(typeof(ChoNotNullOrWhiteSpaceValidator))]
[ChoValidator(typeof(StringValidator), ConstructorArgsText = "10")]
public string XmlFilePath
{
get;
set;
}
[ChoCommandLineArg("o", Description = "The output directory to create files in. The default is the current directory.")]
[ChoStringValidator(MinLength = 10)]
[ChoContainsCharactersValidator("A")]
public string OutputDirectory
{
get;
set;
}
}
10.2 Callback Mechanism
In cases you want to perform some complex validation on members, you can do so with this mechanism. Simply override OnAfterCommandLineArgLoaded method in your command line class as below
Listing 10.6 CommandLine argument object with custom validation
[ChoCommandLineArgObject(Description = "Utility to generate schema or class files from given source.")]
public sealed class ChoAppCmdLineParams1 : ChoCommandLineArgObject
{
[ChoPositionalCommandLineArg(1, "xmlfile", IsRequired = true, Description = "Name of an xml file to infer xsd schema from.")]
[ChoValidator(typeof(ChoNotNullOrWhiteSpaceValidator))]
[ChoValidator(typeof(StringValidator), ConstructorArgsText = "10")]
public string XmlFilePath
{
get;
set;
}
[ChoCommandLineArg("o", Description = "The output directory to create files in. The default is the current directory.")]
[ChoStringValidator(MinLength = 10)]
[ChoContainsCharactersValidator("A")]
public string OutputDirectory
{
get;
set;
}
protected override void OnAfterCommandLineArgLoaded(string memberName, object value)
{
if (memberName == "OutputDirectory")
{
if (!((string)value).StartsWith(@"C:\"))
throw new ArgumentException("Invalid directory passed.");
}
else
base.OnAfterCommandLineArgLoaded(memberName, value);
}
}
In the above sample code shows how to validate members using callback mechanism. If the ‘OutputDirectory’ member value does not starts with ‘C:\’, throws an exception.
Listing 10.7 Test1.exe with incorrect output directory value
>Test1.exe "C:\Windows\Systems\cpanal.xml" /o:"D:\Windows\Systems\Xcpanal.xml"
ConsoleApplication2 [Version 1.0.0.0]
Copyright c 2014
Utility to generate schema or class files from given source.
Found exception while loading `o` command line argument.
Invalid directory passed.
ConsoleApplication2.exe xmlfile [/o:<string>]
xmlfile Name of an xml file to infer xsd schema from.
/o The output directory to create files in. The default is the
current directory.
Press any key to continue . . .
If you run the sample with the above argument values, validation failes for ‘OutputDirectory’ member with exception ‘Invalid directory passed.’.
10.3 Property Setter Mechanism
This is one another way to perform complex validation on members. It is exact similar approach as Callback Machanism. In here the validation can be carried out at the property setter for property command line members. See below sample
Listing 10.8 CommandLine argument object with custom validation
[ChoCommandLineArgObject(Description = "Utility to generate schema or class files from given source.")]
public sealed class ChoAppCmdLineParams1 : ChoCommandLineArgObject
{
[ChoPositionalCommandLineArg(1, "xmlfile", IsRequired = true, Description = "Name of an xml file to infer xsd schema from.")]
[ChoValidator(typeof(ChoNotNullOrWhiteSpaceValidator))]
[ChoValidator(typeof(StringValidator), ConstructorArgsText = "10")]
public string XmlFilePath
{
get;
set;
}
private string _outputDirectory;
[ChoCommandLineArg("o", Description = "The output directory to create files in. The default is the current directory.")]
[ChoStringValidator(MinLength = 10)]
[ChoContainsCharactersValidator("A")]
public string OutputDirectory
{
get { return _outputDirectory; }
set
{
if (!value.StartsWith(@"C:\"))
throw new ArgumentException("Invalid directory passed.");
_outputDirectory = value;
}
}
}
In the above sample code shows how to validate members using property setter mechanism. The ‘OutputDirectory’ property validation is handled in property setter. If the value does not starts with ‘C:\’, throws an exception.
Listing 10.9 Test1.exe with incorrect output directory value
>Test1.exe "C:\Windows\Systems\cpanal.xml" /o:"D:\Windows\Systems\Xcpanal.xml"
ConsoleApplication2 [Version 1.0.0.0]
Copyright c 2014
Utility to generate schema or class files from given source.
Found exception while loading `o` command line argument.
Invalid directory passed.
ConsoleApplication2.exe xmlfile [/o:<string>]
xmlfile Name of an xml file to infer xsd schema from.
/o The output directory to create files in. The default is the
current directory.
Press any key to continue . . .
If you run the sample with the above argument values, validation failes for ‘OutputDirectory’ member with exception ‘Invalid directory passed.’.
11. Command Line Object Builder (Grouping)
So far we have learned about defining and consuming individual command line argument object in applications. It best suited for applications with single functionality with the arguments. Some applications performs multiple functions with their own arguments. For example, you have an application which processes data for various input data (network, file, internet etc.) which requires their own respective arguments. It means about having some sort of factory which you can define these contexts with. Basically the first argument would define the context to look up (network, file, internet etc.) then any following arguments would just act as that specific context’s arguments.
‘NET’ dos command is the perfect example of this scenario. If you type ‘net’ produce this
c:\>net
The syntax of this command is:
NET
[ ACCOUNTS | COMPUTER | CONFIG | CONTINUE | FILE | GROUP | HELP |
HELPMSG | LOCALGROUP | PAUSE | SESSION | SHARE | START |
STATISTICS | STOP | TIME | USE | USER | VIEW ]
In the above, ACCOUNTS, COMPUTER, CONFIG etc. are contexts to ‘NET’ command. Each takes their own set of arguments. If you want to see the arguments of ACCOUNTS context, type ‘net ACCOUNTS /?’ as below
c:\>net ACCOUNTS /?
The syntax of this command is:
NET ACCOUNTS
[/FORCELOGOFF:{minutes | NO}] [/MINPWLEN:length]
[/MAXPWAGE:{days | UNLIMITED}] [/MINPWAGE:days]
[/UNIQUEPW:number] [/DOMAIN]
Here I’m going to walk you through mimicing ‘NET’ command with START, COMPUTER, STOP contexts only using Cinchoo library. First define a Command Line Object Builder object as below
11.1 Defining Command Line Argument Builder
First define command line object builder as below
Listing 11.1 Command line argument builder object
[ChoCommandLineArgBuilder]
public class NetCmdBuilder : ChoCommandLineArgBuilder
{
[ChoCommandLineArgBuilderCommand("START", typeof(STARTCmdLineArgObject), Order = 0)]
[ChoCommandLineArgBuilderCommand("STOP", typeof(STOPCmdLineArgObject), Order = 1)]
[ChoCommandLineArgBuilderCommand("COMPUTER", typeof(COMPUTERCmdLineArgObject), Order = -1)]
public NetCmdBuilder()
{
}
}
The code above illustrates about defining command line object builder object. First thing define a builder class (ex. NetCmdBuilder) from ChoCommandLineArgBuilder class, it indicates that this object is a command line argument builder object. And it must be decorated with ChoCommandLineArgBuilderAttribute to complete the definition. Besides that, we need to start defining commands mapping using ChoCommandLineArgBuilderCommandAttribute in the default constructor of the builder. In the above example, the builder defined with 3 commands START, STOP and COMPUTER mapped with STARTCmdLineArgObject, STOPCmdLineArgObject and COMPUTERCmdLineArgObject respectively. The order in the attribute describes about the display order of the commands in the usage text.
Listing 11.2 COMPUTERCmdLineArgObject
public enum Action { ADD, DEL };
[ChoCommandLineArgObject(DoNotShowUsageDetail = true)]
public class COMPUTERCmdLineArgObject : ChoCommandLineArgObject
{
[ChoPositionalCommandLineArg(1, "\\\\computername", IsRequired = true, Order = 0)]
public string ComputerName;
[ChoCommandLineArg("action", IsRequired = true)]
public Action Action;
}
The above command line argument contains two members, ComputerName – positional required argument and Action – an required enum argument. Note, DoNotShowUsageDetail is true tells the framework not to show the details of each member argument in the usage text.
Listing 11.3 STARTCmdLineArgObject
[ChoCommandLineArgObject]
public class STARTCmdLineArgObject : ChoCommandLineArgObject
{
[ChoPositionalCommandLineArg(1, "service")]
public string ServiceName;
}
Listing 11.4 STOPCmdLineArgObject
[ChoCommandLineArgObject(DoNotShowUsageDetail = true)]
public class STOPCmdLineArgObject : ChoCommandLineArgObject
{
[ChoPositionalCommandLineArg(1, "service", IsRequired = true)]
public string ServiceName;
}
Listing 11.5 Main Method
class Program
{
static void Main(string[] args)
{
NetCmdBuilder netCmdBuilder = new NetCmdBuilder();
Console.WriteLine(netCmdBuilder.CommandLineArgObject.ToString());
}
}
Lets start by creating new instance of netCmdBuilder object. Thats all. The framework does the major lifting of the work behind the scene. After successful load of the arguments, CommandLineArgObject member of the builder object is loaded with matched command object based on the context passed to the executable as argument.
Listed below are test runs of the programs with different set of arguments and its output.
Listing 11.6 net.exe with no arguments
c:\>net
The syntax of this command is:
NET [COMPUTER | START | STOP]
Press any key to continue . . .
Listing 11.7 net.exe with COMPUTER context, no computername passed
c:\>net COMPUTER
Missing '\\computername' argument.
NET COMPUTER \\computername {/ADD | /DEL}
Press any key to continue . . .
Listing 11.7 net.exe with COMPUTER context with valid arguments
c:\>net COMPUTER \\NYC123453 /DEL
-- CommadLineObjectBuilderSample.COMPUTERCmdLineArgObject State --
ComputerName: \\NYC123453
Action: DEL
Press any key to continue . . .
In the above sample successful run, netCmdBuilder.CommandLineArgObject is populated with instance of COMPUTERCmdLineArgObject object.
11.2 Attributes
11.2.1 ChoCommandLineArgObjectAttribute
This attribute is applied to the class which will construct the command line argument object for the passed context and load with them the command line arguments. It contains same set of properties as ChoCommandLineArgObjectAttribute. Please refer the section.
11.2.2 ChoCommandLineArgBuilderCommandAttribute
This attribute is applied to the constructor of the builder class to define the mapping of the commands with command line argument classes. Multiple attributes may be used to define the mapping.
Listing 11.8 Sample command line builder object
[ChoCommandLineArgBuilder]
public class NetCmdBuilder : ChoCommandLineArgBuilder
{
[ChoCommandLineArgBuilderCommand("START", typeof(STARTCmdLineArgObject), Order = 0)]
[ChoCommandLineArgBuilderCommand("STOP", typeof(STOPCmdLineArgObject), Order = 1)]
[ChoCommandLineArgBuilderCommand("COMPUTER", typeof(COMPUTERCmdLineArgObject), Order = -1)]
public NetCmdBuilder()
{
}
}
The above code illustrates that the constructor defined with three commands using ChoCommandLineArgBuildCommandAttribute.
- Command – Required. Command name.
- CommandType – Required. A command line argument object type.
- Order – Optional order to display the commands in the usage text.
11.3 Overrrides
11.2.2 GetCommandLineArgObjectType()
This method can be overridden to take control of discovering the command type for the passed command. Usually all the mapping is done using ChoCommandLineArgBuildCommandAttribute in the builder class. Occationally you may want avoid doing so by overriding this method to handle it.
[ChoCommandLineArgBuilder]
public class ChoNETCommandLineArgBuilder : ChoCommandLineArgBuilder
{
[ChoCommandLineArgBuilderCommand("ACCOUNTS", typeof(ChoAppCmdLineParams))]
public ChoNETCommandLineArgBuilder()
{
}
public override Type GetCommandLineArgObjectType(string command)
{
if (command == "COMPUTER")
return typeof(COMPUTERCmdLineArgObject);
else
return base.GetCommandLineArgObjectType(command);
}
}
The above code illustrates how to override GetCommandLineArgObjectType method.
Cinchoo 