CustomAttributeNamedArgument Structure
Represents a named argument of a custom attribute in the reflection-only context.
Assembly: mscorlib (in mscorlib.dll)
| Name | Description | |
|---|---|---|
![]() | CustomAttributeNamedArgument(MemberInfo, CustomAttributeTypedArgument) | Initializes a new instance of the CustomAttributeNamedArgument class, which represents the specified field or property of the custom attribute, and specifies a CustomAttributeTypedArgument object that describes the type and value of the field or property. |
![]() | CustomAttributeNamedArgument(MemberInfo, Object) | Initializes a new instance of the CustomAttributeNamedArgument class, which represents the specified field or property of the custom attribute, and specifies the value of the field or property. |
| Name | Description | |
|---|---|---|
![]() | IsField | Gets a value that indicates whether the named argument is a field. |
![]() | MemberInfo | Gets the attribute member that would be used to set the named argument. |
![]() | MemberName | Gets the name of the attribute member that would be used to set the named argument. |
![]() | TypedValue | Gets a CustomAttributeTypedArgument structure that can be used to obtain the type and value of the current named argument. |
| Name | Description | |
|---|---|---|
![]() | Equals(Object) | Returns a value that indicates whether this instance is equal to a specified object.(Overrides ValueType.Equals(Object).) |
![]() | GetHashCode() | Returns the hash code for this instance.(Overrides ValueType.GetHashCode().) |
![]() | GetType() | |
![]() | ToString() | Returns a string that consists of the argument name, the equal sign, and a string representation of the argument value.(Overrides ValueType.ToString().) |
| Name | Description | |
|---|---|---|
![]() ![]() | Equality(CustomAttributeNamedArgument, CustomAttributeNamedArgument) | Tests whether two CustomAttributeNamedArgument structures are equivalent. |
![]() ![]() | Inequality(CustomAttributeNamedArgument, CustomAttributeNamedArgument) | Tests whether two CustomAttributeNamedArgument 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 a named argument specified for a custom attribute instance, without executing the code of the corresponding property of the custom attribute type. The TypedValue property returns a CustomAttributeTypedArgument structure that contains the type and value of the named argument.
Important |
|---|
Whether an argument is named or positional, you must access its type and value by using the CustomAttributeTypedArgument structure. |
To create instances of the CustomAttributeData class, use the staticGetCustomAttributes 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 information about the custom attributes that were applied to it and to the type and members it contains.
The attribute that is applied to the type demonstrates array properties, with both positional and named arguments.
Imports System Imports System.Reflection Imports System.Collections.Generic Imports System.Collections.ObjectModel ' The example attribute is applied to the assembly. <Assembly:Example(ExampleKind.ThirdKind, Note:="This is a note on the assembly.")> ' An enumeration used by the ExampleAttribute class. Public Enum ExampleKind FirstKind SecondKind ThirdKind FourthKind End Enum ' An example attribute. The attribute can be applied to all ' targets, from assemblies to parameters. ' <AttributeUsage(AttributeTargets.All)> _ Public Class ExampleAttribute Inherits Attribute ' Data for properties. Private kindValue As ExampleKind Private noteValue As String Private arrayStrings() As String Private arrayNumbers() As Integer ' Constructors. The parameterless constructor (.ctor) calls ' the constructor that specifies ExampleKind and an array of ' strings, and supplies the default values. ' Public Sub New(ByVal initKind As ExampleKind, ByVal initStrings() As String) kindValue = initKind arrayStrings = initStrings End Sub Public Sub New(ByVal initKind As ExampleKind) Me.New(initKind, Nothing) End Sub Public Sub New() Me.New(ExampleKind.FirstKind, Nothing) End Sub ' Properties. The Note and Numbers properties must be read/write, so they ' can be used as named parameters. ' Public ReadOnly Property Kind As ExampleKind Get Return kindValue End Get End Property Public ReadOnly Property Strings As String() Get Return arrayStrings End Get End Property Public Property Note As String Get Return noteValue End Get Set noteValue = value End Set End Property Public Property Numbers As Integer() Get Return arrayNumbers End Get Set arrayNumbers = value End Set End Property End Class ' The example attribute is applied to the test class. ' <Example(ExampleKind.SecondKind, _ New 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 := New Integer() { 53, 57, 59 })> _ Public Class Test ' 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.")> _ Public Sub TestMethod(<Example()> ByVal arg As Object) End Sub ' Sub 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. ' Public Shared Sub Main() Dim asm As [Assembly] = Assembly.ReflectionOnlyLoad("source") Dim t As Type = asm.GetType("Test") Dim m As MethodInfo = t.GetMethod("TestMethod") Dim p() As ParameterInfo = m.GetParameters() Console.WriteLine(vbCrLf & "Attributes for assembly: '{0}'", asm) ShowAttributeData(CustomAttributeData.GetCustomAttributes(asm)) Console.WriteLine(vbCrLf & "Attributes for type: '{0}'", t) ShowAttributeData(CustomAttributeData.GetCustomAttributes(t)) Console.WriteLine(vbCrLf & "Attributes for member: '{0}'", m) ShowAttributeData(CustomAttributeData.GetCustomAttributes(m)) Console.WriteLine(vbCrLf & "Attributes for parameter: '{0}'", p) ShowAttributeData(CustomAttributeData.GetCustomAttributes(p(0))) End Sub Private Shared Sub ShowAttributeData( _ ByVal attributes As IList(Of CustomAttributeData)) For Each cad As CustomAttributeData _ In CType(attributes, IEnumerable(Of CustomAttributeData)) Console.WriteLine(" {0}", cad) Console.WriteLine(" Constructor: '{0}'", cad.Constructor) Console.WriteLine(" Constructor arguments:") For Each cata As CustomAttributeTypedArgument _ In CType(cad.ConstructorArguments, IEnumerable(Of CustomAttributeTypedArgument)) ShowValueOrArray(cata) Next Console.WriteLine(" Named arguments:") For Each cana As CustomAttributeNamedArgument _ In CType(cad.NamedArguments, IEnumerable(Of CustomAttributeNamedArgument)) Console.WriteLine(" MemberInfo: '{0}'", _ cana.MemberInfo) ShowValueOrArray(cana.TypedValue) Next Next End Sub Private Shared Sub ShowValueOrArray(ByVal cata As CustomAttributeTypedArgument) If cata.Value.GetType() Is GetType(ReadOnlyCollection(Of CustomAttributeTypedArgument)) Then Console.WriteLine(" Array of '{0}':", cata.ArgumentType) For Each cataElement As CustomAttributeTypedArgument In cata.Value Console.WriteLine(" Type: '{0}' Value: '{1}'", _ cataElement.ArgumentType, cataElement.Value) Next Else Console.WriteLine(" Type: '{0}' Value: '{1}'", _ cata.ArgumentType, cata.Value) End If End Sub End Class ' 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:
Available since 8
.NET Framework
Available since 2.0
Portable Class Library
Supported in: portable .NET platforms
Windows Phone Silverlight
Available since 8.0
Windows Phone
Available since 8.1
Any public static ( Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.




