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CustomAttributeTypedArgument::Value Property

Gets the value of the argument for a simple argument or for an element of an array argument; gets a collection of values for an array argument.

Namespace:  System.Reflection
Assembly:  mscorlib (in mscorlib.dll)

public:
property Object^ Value {
	Object^ get ();
}

Property Value

Type: System::Object
An object that represents the value of the argument or element, or a generic ReadOnlyCollection<T> of CustomAttributeTypedArgument objects that represent the values of an array-type argument.

If the CustomAttributeTypedArgument represents an array argument, this property returns a ReadOnlyCollection<CustomAttributeTypedArgument> (ReadOnlyCollection(Of CustomAttributeTypedArgument) in Visual Basic). Each element of the collection represents the corresponding element of the array argument.

The type of the value can be obtained by using the ArgumentType property. ArgumentType gets the actual type of the value returned by the Value property for simple arguments or for elements of array arguments. It returns the array type for array arguments.

The following example defines a custom attribute with four constructors and four properties. Two of the properties are read-only, and are set by using the positional parameters of the constructors. The other two properties are read/write, and can be set only by using named arguments. One positional property is an array of strings, and one named property is an array of integers.

The attribute is applied to the assembly, to a type declared in the assembly, to a method of the type, and to a parameter of the method. Different constructors are used for these cases. When executed, the assembly loads itself into the reflection-only context and displays the custom attributes.

The attribute that is applied to the type demonstrates array properties, with both positional and named arguments.

The Value property is used in the ShowValueOrArray method that displays custom attribute data, to display the values of attributes.

using namespace System;
using namespace System::Reflection;
using namespace System::Collections::Generic;
using namespace System::Collections::ObjectModel;

// An enumeration used by the ExampleAttribute class. 
public enum class ExampleKind
{
   FirstKind, SecondKind, ThirdKind, FourthKind
};

// An example attribute. The attribute can be applied to all 
// targets, from assemblies to parameters. 
//
[AttributeUsage(AttributeTargets::All)]
public ref class ExampleAttribute: public Attribute
{
private:
   // Data for properties.
   ExampleKind kindValue;
   String^ noteValue;
   array<String^>^ arrayStrings;
   array<int>^ arrayNumbers;

   // Constructors.  
   void ExampleAttributeInitialize( ExampleKind initKind, array<String^>^ initStrings )
   {
      kindValue = initKind;
      arrayStrings = initStrings;
   }
public:
   ExampleAttribute()
   {
      ExampleAttributeInitialize( ExampleKind::FirstKind, nullptr );
   }
   ExampleAttribute( ExampleKind initKind )
   {
      ExampleAttributeInitialize( initKind, nullptr );
   }
   ExampleAttribute( ExampleKind initKind, array<String^>^ initStrings )
   {
      ExampleAttributeInitialize( initKind, initStrings );
   }

   // Properties. The Note and Numbers properties must be read/write, so they 
   // can be used as named parameters. 
   // 
   property ExampleKind Kind 
   {
      ExampleKind get()
      {
         return kindValue;
      }
   }
   property array<String^>^ Strings
   {
      array<String^>^ get()
      {
         return arrayStrings;
      }
   }
   property String^ Note 
   {
      String^ get()
      {
         return noteValue;
      }

      void set( String^ value )
      {
         noteValue = value;
      }
   }
   property array<int>^ Numbers
   {
      array<int>^ get()
      {
         return arrayNumbers;
      }

      void set( array<int>^ value )
      {
         arrayNumbers = value;
      }
   }
};

// The example attribute is applied to the assembly.
[assembly:Example(ExampleKind::ThirdKind,Note="This is a note on the assembly.")];

// The example attribute is applied to the test class. 
//
[Example(ExampleKind::SecondKind, 
         gcnew array<String^> { "String array argument, line 1", 
                        "String array argument, line 2", 
                        "String array argument, line 3" }, 
         Note="This is a note on the class.",
         Numbers = gcnew array<int> { 53, 57, 59 })] 
public ref class Test
{
public:
   // The example attribute is applied to a method, using the 
   // parameterless constructor and supplying a named argument. 
   // The attribute is also applied to the method parameter. 
   //
   [Example(Note="This is a note on a method.")]
   void TestMethod( [Example] Object^ arg ){}

   // Main() gets objects representing the assembly, the test 
   // type, the test method, and the method parameter. Custom 
   // attribute data is displayed for each of these. 
   // 
   static void Main()
   {
      Assembly^ assembly = Assembly::ReflectionOnlyLoad( "Source" );
      Type^ t = assembly->GetType( "Test" );
      MethodInfo^ m = t->GetMethod( "TestMethod" );
      array<ParameterInfo^>^p = m->GetParameters();

      Console::WriteLine( "\r\nAttributes for assembly: '{0}'", assembly );
      ShowAttributeData( CustomAttributeData::GetCustomAttributes( assembly ) );
      Console::WriteLine( "\r\nAttributes for type: '{0}'", t );
      ShowAttributeData( CustomAttributeData::GetCustomAttributes( t ) );
      Console::WriteLine( "\r\nAttributes for member: '{0}'", m );
      ShowAttributeData( CustomAttributeData::GetCustomAttributes( m ) );
      Console::WriteLine( "\r\nAttributes for parameter: '{0}'", p );
      ShowAttributeData( CustomAttributeData::GetCustomAttributes( p[ 0 ] ) );
   }

private:
    static void ShowValueOrArray(CustomAttributeTypedArgument^ cata)
    {
        if (cata->Value->GetType() == ReadOnlyCollection<CustomAttributeTypedArgument>::typeid)
        {
            Console::WriteLine("         Array of '{0}':", cata->ArgumentType);

            for each (CustomAttributeTypedArgument^ cataElement in 
                (ReadOnlyCollection<CustomAttributeTypedArgument>^) cata->Value)
            {
                Console::WriteLine("             Type: '{0}'  Value: '{1}'",
                    cataElement->ArgumentType, cataElement->Value);
            }
        }
        else
        {
            Console::WriteLine( "         Type: '{0}'  Value: '{1}'",
               cata->ArgumentType, cata->Value );
        }
    }

   static void ShowAttributeData( IList< CustomAttributeData^ >^ attributes )
   {
      for each ( CustomAttributeData^ cad in attributes )
      {
         Console::WriteLine( "   {0}", cad );
         Console::WriteLine( "      Constructor: '{0}'", cad->Constructor );

         Console::WriteLine( "      Constructor arguments:" );
         for each ( CustomAttributeTypedArgument^ cata in cad->ConstructorArguments )
         {
            ShowValueOrArray(cata);
         }

         Console::WriteLine( "      Named arguments:" );
         for each ( CustomAttributeNamedArgument cana in cad->NamedArguments )
         {
            Console::WriteLine( "         MemberInfo: '{0}'", cana.MemberInfo );
            ShowValueOrArray(cana.TypedValue);
         }
      }
   }
};

int main()
{
   Test::Main();
}

/* This code example produces output similar to the following:

Attributes for assembly: 'source, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null'
   [System.Runtime.CompilerServices.CompilationRelaxationsAttribute((Int32)8)]
      Constructor: 'Void .ctor(Int32)'
      Constructor arguments:
         Type: 'System.Int32'  Value: '8'
      Named arguments:
   [System.Runtime.CompilerServices.RuntimeCompatibilityAttribute(WrapNonExceptionThrows = True)]
      Constructor: 'Void .ctor()'
      Constructor arguments:
      Named arguments:
         MemberInfo: 'Boolean WrapNonExceptionThrows'
         Type: 'System.Boolean'  Value: 'True'
   [ExampleAttribute((ExampleKind)2, Note = "This is a note on the assembly.")]
      Constructor: 'Void .ctor(ExampleKind)'
      Constructor arguments:
         Type: 'ExampleKind'  Value: '2'
      Named arguments:
         MemberInfo: 'System.String Note'
         Type: 'System.String'  Value: 'This is a note on the assembly.'

Attributes for type: 'Test'
   [ExampleAttribute((ExampleKind)1, new String[3] { "String array argument, line 1", "String array argument, line 2", "String array argument, line 3" }, Note = "This is a note on the class.", Numbers = new Int32[3] { 53, 57, 59 })]
      Constructor: 'Void .ctor(ExampleKind, System.String[])'
      Constructor arguments:
         Type: 'ExampleKind'  Value: '1'
         Array of 'System.String[]':
             Type: 'System.String'  Value: 'String array argument, line 1'
             Type: 'System.String'  Value: 'String array argument, line 2'
             Type: 'System.String'  Value: 'String array argument, line 3'
      Named arguments:
         MemberInfo: 'System.String Note'
         Type: 'System.String'  Value: 'This is a note on the class.'
         MemberInfo: 'Int32[] Numbers'
         Array of 'System.Int32[]':
             Type: 'System.Int32'  Value: '53'
             Type: 'System.Int32'  Value: '57'
             Type: 'System.Int32'  Value: '59'

Attributes for member: 'Void TestMethod(System.Object)'
   [ExampleAttribute(Note = "This is a note on a method.")]
      Constructor: 'Void .ctor()'
      Constructor arguments:
      Named arguments:
         MemberInfo: 'System.String Note'
         Type: 'System.String'  Value: 'This is a note on a method.'

Attributes for parameter: 'System.Object arg'
   [ExampleAttribute()]
      Constructor: 'Void .ctor()'
      Constructor arguments:
      Named arguments:
*/

ArgumentType | ReflectionOnlyLoad

.NET Framework

Supported in: 4.5.2, 4.5.1, 4.5, 4, 3.5, 3.0, 2.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

.NET for Windows Store apps

Supported in: Windows 8

.NET for Windows Phone apps

Supported in: Windows Phone 8.1, Windows Phone 8, Silverlight 8.1

Windows Phone 8.1, Windows Phone 8, Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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