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CustomAttributeData.ConstructorArguments Property

Gets the list of positional arguments specified for the attribute instance represented by the CustomAttributeData object.

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

'Declaration
<ComVisibleAttribute(True)> _
Public Overridable ReadOnly Property ConstructorArguments As IList(Of CustomAttributeTypedArgument)

Property Value

Type: System.Collections.Generic.IList(Of CustomAttributeTypedArgument)
A collection of structures that represent the positional arguments specified for the custom attribute instance.

This method gets the positional arguments that were specified for the custom attribute instance without executing any of the custom attribute code. Thus, it can be used in the reflection-only context.

Use the NamedArguments method to get the named arguments specified for the attribute instance.

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 ConstructorArguments property is used in the ShowAttributeData method that displays custom attribute data. In this code example, this property is used to display the list of arguments passed to the constructor that initialized the attribute.

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:

.NET Framework

Supported in: 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 Silverlight 8.1, Windows Phone Silverlight 8

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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