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Attribute.Equals Method

Microsoft Silverlight will reach end of support after October 2021. Learn more.

This API supports the .NET Framework infrastructure and is not intended to be used directly from your code.

Returns a value that indicates whether this instance is equal to a specified object.

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

Syntax

'Declaration
Public Overrides Function Equals ( _
    obj As Object _
) As Boolean
public override bool Equals(
    Object obj
)

Parameters

  • obj
    Type: System.Object
    An Object to compare with this instance or nulla null reference (Nothing in Visual Basic).

Return Value

Type: System.Boolean
true if obj equals the type and value of this instance; otherwise, false.

Examples

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
// Example for the Attribute.Equals( object ) method.
using System;
using System.Reflection;

// Define a custom parameter attribute that takes a single message argument.
[AttributeUsage(AttributeTargets.Parameter)]
public class ArgumentUsageAttribute : Attribute
{
    // This is the attribute constructor.
    public ArgumentUsageAttribute(string UsageMsg)
    {
        this.usageMsg = UsageMsg;
    }

    // usageMsg is storage for the attribute message.
    protected string usageMsg;

    // Override ToString() to append the message to what the base generates.
    public override string ToString()
    {
        return base.ToString() + ":" + usageMsg;
    }
}

// Define a custom parameter attribute that generates
// a GUID for each instance.
[AttributeUsage(AttributeTargets.Parameter)]
public class ArgumentIDAttribute : Attribute
{
    // This is the attribute constructor, which generates the GUID.
    public ArgumentIDAttribute()
    {
        this.instanceGUID = Guid.NewGuid();
    }

    // instanceGUID is storage for the generated GUID.
    protected Guid instanceGUID;

    // Override ToString() to append the GUID to what the base generates.
    public override string ToString()
    {
        return base.ToString() + "." + instanceGUID.ToString();
    }
}

public class TestClass
{
    // Assign an ArgumentID attribute to each parameter.
    // Assign an ArgumentUsage attribute to each parameter.
    public void TestMethod(
        [ArgumentID]
        [ArgumentUsage("Must pass an array here.")]
        String[] strArray,
        [ArgumentID]
        [ArgumentUsage("Can pass param list or array here.")]
        params String[] strList)
    { }
}

class Example
{
    // Create Attribute objects and compare them.
    public static void Demo(System.Windows.Controls.TextBlock outputBlock)
    {
        outputBlock.Text += "This example of Attribute.Equals( object ) " +
            "generates the following output." + "\n";

        // Get the class type, and then get the MethodInfo object
        // for TestMethod to access its metadata.
        Type clsType = typeof(TestClass);
        MethodInfo mInfo = clsType.GetMethod("TestMethod");

        // There will be two elements in pInfoArray, one for each parameter.
        ParameterInfo[] pInfoArray = mInfo.GetParameters();
        if (pInfoArray != null)
        {
            // Create an instance of the argument usage attribute on strArray.
            ArgumentUsageAttribute arrayUsageAttr1 = (ArgumentUsageAttribute)
                Attribute.GetCustomAttribute(pInfoArray[0],
                    typeof(ArgumentUsageAttribute));

            // Create another instance of the argument usage attribute
            // on strArray.
            ArgumentUsageAttribute arrayUsageAttr2 = (ArgumentUsageAttribute)
                Attribute.GetCustomAttribute(pInfoArray[0],
                    typeof(ArgumentUsageAttribute));

            // Create an instance of the argument usage attribute on strList.
            ArgumentUsageAttribute listUsageAttr = (ArgumentUsageAttribute)
                Attribute.GetCustomAttribute(pInfoArray[1],
                    typeof(ArgumentUsageAttribute));

            // Create an instance of the argument ID attribute on strArray.
            ArgumentIDAttribute arrayIDAttr1 = (ArgumentIDAttribute)
                Attribute.GetCustomAttribute(pInfoArray[0],
                    typeof(ArgumentIDAttribute));

            // Create another instance of the argument ID attribute on strArray.
            ArgumentIDAttribute arrayIDAttr2 = (ArgumentIDAttribute)
                Attribute.GetCustomAttribute(pInfoArray[0],
                    typeof(ArgumentIDAttribute));

            // Create an instance of the argument ID attribute on strList.
            ArgumentIDAttribute listIDAttr = (ArgumentIDAttribute)
                Attribute.GetCustomAttribute(pInfoArray[1],
                    typeof(ArgumentIDAttribute));

            // Compare various pairs of attributes for equality.
            outputBlock.Text += "\nCompare a usage attribute instance to " +
                "another instance of the same attribute:" + "\n";
            outputBlock.Text += String.Format("   \"{0}\" == \n   \"{1}\" ? {2}",
                arrayUsageAttr1.ToString(), arrayUsageAttr2.ToString(),
                arrayUsageAttr1.Equals(arrayUsageAttr2)) + "\n";

            outputBlock.Text += String.Format("\nCompare a usage attribute to " +
                "another usage attribute:") + "\n";
            outputBlock.Text += String.Format("   \"{0}\" == \n   \"{1}\" ? {2}",
                arrayUsageAttr1.ToString(), listUsageAttr.ToString(),
                arrayUsageAttr1.Equals(listUsageAttr)) + "\n";

            outputBlock.Text += String.Format("\nCompare an ID attribute instance to " +
                "another instance of the same attribute:") + "\n";
            outputBlock.Text += String.Format("   \"{0}\" == \n   \"{1}\" ? {2}",
                arrayIDAttr1.ToString(), arrayIDAttr2.ToString(),
                arrayIDAttr1.Equals(arrayIDAttr2)) + "\n";

            outputBlock.Text += "\nCompare an ID attribute to another ID attribute:" + "\n";
            outputBlock.Text += String.Format("   \"{0}\" == \n   \"{1}\" ? {2}",
                arrayIDAttr1.ToString(), listIDAttr.ToString(),
                arrayIDAttr1.Equals(listIDAttr)) + "\n";
        }
        else
            outputBlock.Text += String.Format("The parameters information could " +
                "not be retrieved for method {0}.", mInfo.Name) + "\n";
    }
}

/*
This example of Attribute.Equals( object ) generates the following output.

Compare a usage attribute instance to another instance of the same attribute:
   "ArgumentUsageAttribute:Must pass an array here." ==
   "ArgumentUsageAttribute:Must pass an array here." ? True

Compare a usage attribute to another usage attribute:
   "ArgumentUsageAttribute:Must pass an array here." ==
   "ArgumentUsageAttribute:Can pass param list or array here." ? False

Compare an ID attribute instance to another instance of the same attribute:
   "ArgumentIDAttribute.06abf046-0c38-47ac-b215-09e1daa7f37d" ==
   "ArgumentIDAttribute.cea23c39-f14b-4e95-bee2-9f661d8cd64b" ? False

Compare an ID attribute to another ID attribute:
   "ArgumentIDAttribute.06abf046-0c38-47ac-b215-09e1daa7f37d" ==
   "ArgumentIDAttribute.bdeb6f3e-18aa-410b-bef6-9788956b008c" ? False
*/

Version Information

Silverlight

Supported in: 5, 4, 3

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0

XNA Framework

Supported in: Xbox 360, Windows Phone OS 7.0

Platforms

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.

See Also

Reference