Indicates to compilers that a method call or attribute should be ignored unless a specified conditional compilation symbol is defined.
Assembly: mscorlib (in mscorlib.dll)
Thetype exposes the following members.
|Equals||Infrastructure. Returns a value that indicates whether this instance is equal to a specified object. (Inherited from Attribute.)|
|Finalize||Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection. (Inherited from Object.)|
|GetHashCode||Returns the hash code for this instance. (Inherited from Attribute.)|
|GetType||Gets the Type of the current instance. (Inherited from Object.)|
|IsDefaultAttribute||When overridden in a derived class, indicates whether the value of this instance is the default value for the derived class. (Inherited from Attribute.)|
|Match||When overridden in a derived class, returns a value that indicates whether this instance equals a specified object. (Inherited from Attribute.)|
|MemberwiseClone||Creates a shallow copy of the current Object. (Inherited from Object.)|
|ToString||Returns a string that represents the current object. (Inherited from Object.)|
|_Attribute.GetIDsOfNames||Maps a set of names to a corresponding set of dispatch identifiers. (Inherited from Attribute.)|
|_Attribute.GetTypeInfo||Retrieves the type information for an object, which can be used to get the type information for an interface. (Inherited from Attribute.)|
|_Attribute.GetTypeInfoCount||Retrieves the number of type information interfaces that an object provides (either 0 or 1). (Inherited from Attribute.)|
|_Attribute.Invoke||Provides access to properties and methods exposed by an object. (Inherited from Attribute.)|
You can apply the attribute to methods and classes. However, its use on classes is valid only for types that are derived from Attribute. either will be ignored or will produce a compiler warning or error message if you apply it to any other type.
In the .NET Framework versions 1.0 and 1.1, the attribute can be applied only to methods.
Applying 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 with is defined. You will get a compilation error in Visual Studio if you apply this attribute to a method that does not return void. Applying 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:
Compiler command-line options (for example, /define:DEBUG).
Environment variables in the operating system shell (for example, set DEBUG=1).
Pragmas in the source code (for example, #define DEBUG to define the compilation variable and #undef DEBUG to undefine it).
Compilers that comply with the Common Language Specification (CLS) are permitted to ignore . The C#, J#, and Visual Basic compilers support ; the C++ and JScript compilers do not support the attribute.
For more information about how to use attributes, see Extending Metadata Using Attributes.
The following code example demonstrates the use of . The example assumes that the condition is defined in the /define compiler option. You can obtain different results by changing the compiler option. You can optionally define the conditions in the sample code instead of identifying them as compiler options.
#Const CONDITION1 = True #Const CONDITION2 = True Imports System Imports System.Diagnostics Class 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
Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2