ConditionalAttribute Class

Definition

public ref class ConditionalAttribute sealed : Attribute

[System.AttributeUsage(System.AttributeTargets.Class | System.AttributeTargets.Method, AllowMultiple=true)]public sealed class ConditionalAttribute : Attribute

[System.AttributeUsage(System.AttributeTargets.Method, AllowMultiple=true)][System.Serializable]public sealed class ConditionalAttribute : Attribute

[System.AttributeUsage(System.AttributeTargets.Class | System.AttributeTargets.Method, AllowMultiple=true)][System.Serializable][System.Runtime.InteropServices.ComVisible(true)]public sealed class ConditionalAttribute : Attribute

[<System.AttributeUsage(System.AttributeTargets.Class | System.AttributeTargets.Method, AllowMultiple=true)>]type ConditionalAttribute = class    inherit Attribute

[<System.AttributeUsage(System.AttributeTargets.Method, AllowMultiple=true)>][<System.Serializable>]type ConditionalAttribute = class    inherit Attribute

[<System.AttributeUsage(System.AttributeTargets.Class | System.AttributeTargets.Method, AllowMultiple=true)>][<System.Serializable>][<System.Runtime.InteropServices.ComVisible(true)>]type ConditionalAttribute = class    inherit Attribute

Public NotInheritable Class ConditionalAttributeInherits Attribute

Inheritance

Object

Attribute

ConditionalAttribute

Attributes

AttributeUsageAttributeSerializableAttributeComVisibleAttribute

Examples

The following example demonstrates the use ofConditionalAttribute. The example assumes that the condition is defined with the/define compiler option. You can obtain different results by changing the compiler option. You can optionally define the conditions by using pragmas in the sample code instead of identifying them as compiler options.

#define CONDITION1#define CONDITION2using System;using System.Diagnostics;class Test{    static void Main()    {        Console.WriteLine("Calling Method1");        Method1(3);        Console.WriteLine("Calling Method2");        Method2();        Console.WriteLine("Using the Debug class");        Debug.Listeners.Add(new ConsoleTraceListener());        Debug.WriteLine("DEBUG is defined");    }    [Conditional("CONDITION1")]    public static void Method1(int x)    {        Console.WriteLine("CONDITION1 is defined");    }    [Conditional("CONDITION1"), Conditional("CONDITION2")]    public static void Method2()    {        Console.WriteLine("CONDITION1 or CONDITION2 is defined");    }}/*When compiled as shown, the application (named ConsoleApp)produces the following output.Calling Method1CONDITION1 is definedCalling Method2CONDITION1 or CONDITION2 is definedUsing the Debug classDEBUG is defined*/

#Const CONDITION1 = True#Const CONDITION2 = TrueImports System.DiagnosticsClass Test    Shared Sub Main()        Console.WriteLine("Calling Method1")        Method1(3)        Console.WriteLine("Calling Method2")        Method2()                Console.WriteLine("Using the Debug class")        Debug.Listeners.Add(New ConsoleTraceListener())        Debug.WriteLine("DEBUG is defined")    End Sub           <ConditionalAttribute("CONDITION1")> _    Shared Sub Method1(x As Integer)        Console.WriteLine("CONDITION1 is defined")    End Sub        <ConditionalAttribute("CONDITION1"), ConditionalAttribute("CONDITION2")> _    Shared Sub Method2()        Console.WriteLine("CONDITION1 or CONDITIOIN2 is defined")    End Sub    End Class' When compiled as shown, the application (named ConsoleApp) ' produces the following output.'Calling Method1'CONDITION1 is defined'Calling Method2'CONDITION1 or CONDITION2 is defined'Using the Debug class'DEBUG is defined

Remarks

You can apply theConditionalAttribute attribute to methods and classes. However, its use on classes is valid only for types that are derived fromAttribute.ConditionalAttribute either will be ignored or will produce a compiler warning or error message if you apply it to any other type.

ApplyingConditionalAttribute to a method indicates to compilers that a call to the method should not be compiled into Microsoft intermediate language (MSIL) unless the conditional compilation symbol that is associated withConditionalAttribute is defined. You will get a compilation error in Visual Studio if you apply this attribute to a method that does not return void. ApplyingConditionalAttribute to an attribute indicates that the attribute should not be emitted to metadata unless the conditional compilation symbol is defined. Any arguments passed to the method or attribute are still type-checked by the compiler.

You can use the following techniques to define conditional compilation symbols:

• Use compiler command-line options; for example,/define:DEBUG.

• Use environment variables in the operating system shell; for example,set DEBUG=1.

• Use pragmas in the source code; for example, define the compilation variable as follows:

  #define DEBUG

  #Const DEBUG=True

  To undefine the variable, use the following:

  #undef DEBUG

  #Const DEBUG=False

Compilers that comply with the Common Language Specification (CLS) are permitted to ignoreConditionalAttribute. The C#, F#, Visual Basic, and C++ compilers supportConditionalAttribute; the JScript compiler does not support the attribute.

ConditionalAttribute is applied to the methods that are defined in theDebug andTrace classes.

For more information about how to use attributes, seeAttributes.