CustomAttributeTypedArgument.Value 屬性
定義
重要
部分資訊涉及發行前產品,在發行之前可能會有大幅修改。 Microsoft 對此處提供的資訊,不做任何明確或隱含的瑕疵擔保。
針對簡單引數或陣列引數元素取得引數的值;針對陣列引數取得值集合。
public:
property System::Object ^ Value { System::Object ^ get(); };
public object Value { get; }
public object? Value { get; }
member this.Value : obj
Public ReadOnly Property Value As Object
屬性值
表示引數值或元素值的物件,或表示陣列型別引數值之 ReadOnlyCollection<T> 物件的泛型 CustomAttributeTypedArgument。
範例
下列範例會定義具有四個建構函式和四個屬性的自定義屬性。 其中兩個屬性是唯讀的,並使用建構函式的位置參數來設定。 其他兩個屬性是可擦寫的,而且只能藉由使用具名自變數來設定。 一個位置屬性是字串數位,而一個具名屬性是整數陣列。
屬性會套用至組件、組件中宣告的類型、類型的方法,以及方法的參數。 這些案例使用不同的建構函式。 執行時,元件會自行載入僅限反映的內容,並顯示自定義屬性。
套用至型別的屬性會示範數位屬性,其中包含位置自變數和具名自變數。
屬性 Value 用於 ShowValueOrArray
顯示自定義屬性數據的方法中,以顯示屬性值。
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:
*/
using System;
using System.Reflection;
using System.Collections.Generic;
using 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
};
// An example attribute. The attribute can be applied to all
// targets, from assemblies to parameters.
//
[AttributeUsage(AttributeTargets.All)]
public class ExampleAttribute : Attribute
{
// Data for properties.
private ExampleKind kindValue;
private string noteValue;
private string[] arrayStrings;
private int[] arrayNumbers;
// Constructors. The parameterless constructor (.ctor) calls
// the constructor that specifies ExampleKind and an array of
// strings, and supplies the default values.
//
public ExampleAttribute(ExampleKind initKind, string[] initStrings)
{
kindValue = initKind;
arrayStrings = initStrings;
}
public ExampleAttribute(ExampleKind initKind) : this(initKind, null) {}
public ExampleAttribute() : this(ExampleKind.FirstKind, null) {}
// Properties. The Note and Numbers properties must be read/write, so they
// can be used as named parameters.
//
public ExampleKind Kind { get { return kindValue; }}
public string[] Strings { get { return arrayStrings; }}
public string Note
{
get { return noteValue; }
set { noteValue = value; }
}
public int[] Numbers
{
get { return arrayNumbers; }
set { arrayNumbers = value; }
}
}
// 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 int[] { 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 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.
//
public static void Main()
{
Assembly asm = Assembly.ReflectionOnlyLoad("Source");
Type t = asm.GetType("Test");
MethodInfo m = t.GetMethod("TestMethod");
ParameterInfo[] p = m.GetParameters();
Console.WriteLine("\r\nAttributes for assembly: '{0}'", asm);
ShowAttributeData(CustomAttributeData.GetCustomAttributes(asm));
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 ShowAttributeData(
IList<CustomAttributeData> attributes)
{
foreach( CustomAttributeData cad in attributes )
{
Console.WriteLine(" {0}", cad);
Console.WriteLine(" Constructor: '{0}'", cad.Constructor);
Console.WriteLine(" Constructor arguments:");
foreach( CustomAttributeTypedArgument cata
in cad.ConstructorArguments )
{
ShowValueOrArray(cata);
}
Console.WriteLine(" Named arguments:");
foreach( CustomAttributeNamedArgument cana
in cad.NamedArguments )
{
Console.WriteLine(" MemberInfo: '{0}'",
cana.MemberInfo);
ShowValueOrArray(cana.TypedValue);
}
}
}
private static void ShowValueOrArray(CustomAttributeTypedArgument cata)
{
if (cata.Value.GetType() == typeof(ReadOnlyCollection<CustomAttributeTypedArgument>))
{
Console.WriteLine(" Array of '{0}':", cata.ArgumentType);
foreach (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);
}
}
}
/* 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:
*/
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:
ArgumentType | ReflectionOnlyLoad
備註
CustomAttributeTypedArgument如果 代表陣組自變數,則此屬性會ReadOnlyCollection<CustomAttributeTypedArgument>
傳回Visual Basic) 中的 (ReadOnlyCollection(Of CustomAttributeTypedArgument)
。 集合的每個專案都代表陣列自變數的對應專案。
您可以使用 屬性來取得 ArgumentType 值的型別。 ArgumentType 會取得屬性針對簡單自變數或數位自變數的專案所 Value 傳回之值的實際型別。 它會傳回數位自變數的數位型態。