Attribute.Equals Method
This API supports the .NET Framework infrastructure and is not intended to be used directly from your code.
[ This article is for Windows Phone 8 developers. If you’re developing for Windows 10, see the latest documentation. ]
Returns a value that indicates whether this instance is equal to a specified object.
Assembly: mscorlib (in mscorlib.dll)
Parameters
- obj
- Type: System.Object
An Object to compare with this instance or Nothing.
Return Value
Type: System.Booleantrue if obj equals the type and value of this instance; otherwise, false.
The following code example defines two custom parameter Attribute classes, then creates several objects of each class and shows the use of the Equals method to compare them.
' Example for the Attribute.Equals( Object ) method. Imports System.Reflection ' Define a custom parameter attribute that takes a single message argument. <AttributeUsage(AttributeTargets.Parameter)> _ Public Class ArgumentUsageAttribute Inherits Attribute ' This is the attribute constructor. Public Sub New(ByVal UsageMsg As String) Me.usageMsg = UsageMsg End Sub ' New ' usageMsg is storage for the attribute message. Protected usageMsg As String ' Override ToString() to append the message to what the base generates. Public Overrides Function ToString() As String Return MyBase.ToString() + ":" + usageMsg End Function ' ToString End Class ' ArgumentUsageAttribute ' Define a custom parameter attribute that generates a GUID for each instance. <AttributeUsage(AttributeTargets.Parameter)> _ Public Class ArgumentIDAttribute Inherits Attribute ' This is the attribute constructor, which generates the GUID. Public Sub New() Me.GUIDinstance = Guid.NewGuid() End Sub ' New ' instanceGUID is storage for the generated GUID. Protected GUIDinstance As Guid ' Override ToString() to append the GUID to what the base generates. Public Overrides Function ToString() As String Return MyBase.ToString() + "." + GUIDinstance.ToString() End Function ' ToString End Class ' ArgumentIDAttribute Public Class TestClass ' Assign an ArgumentID attribute to each parameter. ' Assign an ArgumentUsage attribute to each parameter. Public Sub TestMethod( _ <ArgumentID(), ArgumentUsage("Must pass an array here.")> ByVal _ strArray() As String, _ <ArgumentID(), ArgumentUsage("Can pass param list or array here.")> ByVal _ ParamArray strList() As String) End Sub ' TestMethod End Class ' TestClass Module Example ' Create Attribute objects and compare them. Sub CompareAttributes(ByVal outputBlock As System.Windows.Controls.TextBlock) ' Get the class type, and then get the MethodInfo object ' for TestMethod to access its metadata. Dim clsType As Type = GetType(TestClass) Dim mInfo As MethodInfo = clsType.GetMethod("TestMethod") ' There will be two elements in pInfoArray, one for each parameter. Dim pInfoArray As ParameterInfo() = mInfo.GetParameters() If Not (pInfoArray Is Nothing) Then ' Create an instance of the argument usage attribute on strArray. Dim arrayUsageAttr1 As ArgumentUsageAttribute = _ Attribute.GetCustomAttribute(pInfoArray(0), _ GetType(ArgumentUsageAttribute)) ' Create another instance of the argument usage attribute ' on strArray. Dim arrayUsageAttr2 As ArgumentUsageAttribute = _ Attribute.GetCustomAttribute(pInfoArray(0), _ GetType(ArgumentUsageAttribute)) ' Create an instance of the argument usage attribute on strList. Dim listUsageAttr As ArgumentUsageAttribute = _ Attribute.GetCustomAttribute(pInfoArray(1), _ GetType(ArgumentUsageAttribute)) ' Create an instance of the argument ID attribute on strArray. Dim arrayIDAttr1 As ArgumentIDAttribute = _ Attribute.GetCustomAttribute(pInfoArray(0), _ GetType(ArgumentIDAttribute)) ' Create another instance of the argument ID attribute on strArray. Dim arrayIDAttr2 As ArgumentIDAttribute = _ Attribute.GetCustomAttribute(pInfoArray(0), _ GetType(ArgumentIDAttribute)) ' Create an instance of the argument ID attribute on strList. Dim listIDAttr As ArgumentIDAttribute = _ Attribute.GetCustomAttribute(pInfoArray(1), _ GetType(ArgumentIDAttribute)) ' Compare various pairs of attributes for equality. outputBlock.Text &= vbCrLf & "Compare a usage attribute instance " & _ "to another instance of the same attribute:" & vbCrLf outputBlock.Text &= String.Format(" ""{0}"" = " & vbCrLf & " ""{1}"" ? {2}", _ arrayUsageAttr1.ToString(), arrayUsageAttr2.ToString(), _ arrayUsageAttr1.Equals(arrayUsageAttr2)) & vbCrLf outputBlock.Text &= String.Format(vbCrLf & _ "Compare a usage attribute to another usage attribute:") & vbCrLf outputBlock.Text &= String.Format(" ""{0}"" = " & vbCrLf & " ""{1}"" ? {2}", _ arrayUsageAttr1.ToString(), listUsageAttr.ToString(), _ arrayUsageAttr1.Equals(listUsageAttr)) & vbCrLf outputBlock.Text &= String.Format(vbCrLf & "Compare an ID attribute instance " & _ "to another instance of the same attribute:") & vbCrLf outputBlock.Text &= String.Format(" ""{0}"" = " & vbCrLf & " ""{1}"" ? {2}", _ arrayIDAttr1.ToString(), arrayIDAttr2.ToString(), _ arrayIDAttr1.Equals(arrayIDAttr2)) & vbCrLf outputBlock.Text &= String.Format(vbCrLf & _ "Compare an ID attribute to another ID attribute:") & vbCrLf outputBlock.Text &= String.Format(" ""{0}"" = " & vbCrLf & " ""{1}"" ? {2}", _ arrayIDAttr1.ToString(), listIDAttr.ToString(), _ arrayIDAttr1.Equals(listIDAttr)) & vbCrLf Else outputBlock.Text &= String.Format("The parameters information could " & _ "not be retrieved for method {0}.", mInfo.Name) & vbCrLf End If End Sub Public Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock) outputBlock.Text &= "This example of Attribute.Equals( Object ) " & _ "generates the following output." & vbCrLf CompareAttributes(outputBlock) End Sub End Module ' This example of Attribute.Equals( Object ) generates the following output. ' ' Compare a usage attribute instance to another instance of the same attribute: ' "NDP_UE_VB.ArgumentUsageAttribute:Must pass an array here." = ' "NDP_UE_VB.ArgumentUsageAttribute:Must pass an array here." ? True ' ' Compare a usage attribute to another usage attribute: ' "NDP_UE_VB.ArgumentUsageAttribute:Must pass an array here." = ' "NDP_UE_VB.ArgumentUsageAttribute:Can pass param list or array here." ? False ' ' Compare an ID attribute instance to another instance of the same attribute: ' "NDP_UE_VB.ArgumentIDAttribute.aa2c2346-ca87-40d6-afb7-5e3bc1637351" = ' "NDP_UE_VB.ArgumentIDAttribute.4192c26c-9a7b-4a74-97fc-6c3dfbc2cdfe" ? False ' ' Compare an ID attribute to another ID attribute: ' "NDP_UE_VB.ArgumentIDAttribute.aa2c2346-ca87-40d6-afb7-5e3bc1637351" = ' "NDP_UE_VB.ArgumentIDAttribute.237a7337-15f1-469b-a5ce-7503def917b2" ? False
Show: