CustomAttributeTypedArgument Structure
Represents an argument of a custom attribute in the reflection-only context, or an element of an array argument.
Assembly: mscorlib (in mscorlib.dll)
The CustomAttributeTypedArgument type exposes the following members.
| Name | Description | |
|---|---|---|
![]() | CustomAttributeTypedArgument(Object) | Initializes a new instance of the CustomAttributeTypedArgument class with the specified value. |
![]() | CustomAttributeTypedArgument(Type, Object) | Initializes a new instance of the CustomAttributeTypedArgument class with the specified type and value. |
| Name | Description | |
|---|---|---|
![]() | ArgumentType | Gets the type of the argument or of the array argument element. |
![]() | Value | 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. |
| Name | Description | |
|---|---|---|
![]() | Equals | Indicates whether this instance and a specified object are equal. (Overrides ValueType::Equals(Object).) |
![]() | 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. (Overrides ValueType::GetHashCode().) |
![]() | GetType | Gets the Type of the current instance. (Inherited from Object.) |
![]() | MemberwiseClone | Creates a shallow copy of the current Object. (Inherited from Object.) |
![]() | ToString | Returns a string consisting of the argument name, the equal sign, and a string representation of the argument value. (Overrides ValueType::ToString().) |
| Name | Description | |
|---|---|---|
![]() ![]() | Equality | Tests whether two CustomAttributeTypedArgument structures are equivalent. |
![]() ![]() | Inequality | Tests whether two CustomAttributeTypedArgument structures are different. |
Code that is being examined in the reflection-only context cannot be executed, so it is not always possible to examine custom attributes by creating instances of them and then examining their properties, using methods like Attribute::GetCustomAttributes, MemberInfo::GetCustomAttributes, and so on. If the code for the attribute type itself is loaded into the reflection-only context, it cannot be executed.
The CustomAttributeNamedArgument structure is used by the CustomAttributeData class to provide access to the type and value of a positional argument specified for a custom attribute instance, without executing the attribute constructor. It also provides access to the type and value of a named argument without executing the code of the corresponding property of the custom attribute type.
The types and values of all the positional and named arguments of an attribute instance are provided by CustomAttributeTypedArgument structures. The positional attributes returned by the CustomAttributeData::ConstructorArguments property are directly represented by CustomAttributeTypedArgument structures, but the named arguments returned by the CustomAttributeData::NamedArguments property are represented by CustomAttributeNamedArgument structures; to get the CustomAttributeTypedArgument structure for a named argument, use the CustomAttributeNamedArgument::TypedValue property.
If an argument is an array of values, the Value property of the CustomAttributeTypedArgument that represents the argument returns a generic ReadOnlyCollection<T> of CustomAttributeTypedArgument objects. Each CustomAttributeTypedArgument object in the collection represents the corresponding element of the array.
To create instances of the CustomAttributeData class, use the static GetCustomAttributes factory method.
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.
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: */
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
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.
