Attribute.GetCustomAttribute Method (MemberInfo, Type)
Retrieves a custom attribute applied to a member of a type. Parameters specify the member, and the type of the custom attribute to search for.
Assembly: mscorlib (in mscorlib.dll)
Public Shared Function GetCustomAttribute ( element As MemberInfo, attributeType As Type ) As Attribute
Parameters
- element
-
Type:
System.Reflection.MemberInfo
An object derived from the MemberInfo class that describes a constructor, event, field, method, or property member of a class.
- attributeType
-
Type:
System.Type
The type, or a base type, of the custom attribute to search for.
Return Value
Type: System.AttributeA reference to the single custom attribute of type attributeType that is applied to element, or null if there is no such attribute.
| Exception | Condition |
|---|---|
| ArgumentNullException | element or attributeType is null. |
| ArgumentException | attributeType is not derived from Attribute. |
| NotSupportedException | element is not a constructor, method, property, event, type, or field. |
| AmbiguousMatchException | More than one of the requested attributes was found. |
| TypeLoadException | A custom attribute type cannot be loaded. |
A match is determined in the same way described in the Return Value section of Type.IsAssignableFrom.
Note |
|---|
Starting with the .NET Framework version 2.0, this method returns security attributes on types, methods, and constructors if the attributes are stored in the new metadata format. Assemblies compiled with version 2.0 or later use the new format. Dynamic assemblies and assemblies compiled with earlier versions of the .NET Framework use the old XML format. See Emitting Declarative Security Attributes. |
The following code example illustrates the use of the GetCustomAttribute method taking a MemberInfo as a parameter.
Imports System Imports System.Reflection Module DemoModule Public Class TestClass ' Assign the Obsolete attribute to a method. <Obsolete("This method is obsolete. Use Method2() instead.")> _ Public Sub Method1() End Sub Public Sub Method2() End Sub End Class Sub Main() ' Get the class type to access its metadata. Dim clsType As Type = GetType(TestClass) ' Get the MethodInfo object for Method1. Dim mInfo As MethodInfo = clsType.GetMethod("Method1") ' See if the Obsolete attribute is defined for this method. Dim isDef As Boolean = Attribute.IsDefined(mInfo, _ GetType(ObsoleteAttribute)) Dim strDef As String If isDef = True Then strDef = "is" Else strDef = "is not" End If ' Display the results. Console.WriteLine("The Obsolete attribute {0} defined for " & _ "method {1} of class {2}.", strDef, mInfo.Name, clsType.Name) ' If it's defined, display the attribute's message. If isDef = True Then Dim attr As Attribute = Attribute.GetCustomAttribute(mInfo, _ GetType(ObsoleteAttribute)) If Not attr Is Nothing And TypeOf attr Is ObsoleteAttribute Then Dim obsAttr As ObsoleteAttribute = _ CType(attr, ObsoleteAttribute) Console.WriteLine("The message is: ""{0}""", obsAttr.Message) Else Console.WriteLine("The message could not be retrieved.") End If End If End Sub End Module ' Output: ' The Obsolete attribute is defined for method Method1 of class TestClass. ' The message is: "This method is obsolete. Use Method2() instead."
Available since 1.1
Portable Class Library
Supported in: portable .NET platforms
Silverlight
Available since 2.0
Windows Phone Silverlight
Available since 7.0
