Tuple<T1, T2>.IStructuralEquatable.Equals Method
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Returns a value that indicates whether the current Tuple<T1, T2> object is equal to a specified object based on a specified comparison method.
Namespace: System
Assembly: mscorlib (in mscorlib.dll)
Syntax
'Declaration
Private Function Equals ( _
other As Object, _
comparer As IEqualityComparer _
) As Boolean Implements IStructuralEquatable.Equals
bool IStructuralEquatable.Equals(
Object other,
IEqualityComparer comparer
)
Parameters
- other
Type: System.Object
The object to compare with this instance.
- comparer
Type: System.Collections.IEqualityComparer
An object that defines the method to use to evaluate whether the two objects are equal.
Return Value
Type: System.Boolean
true if the current instance is equal to the specified object; otherwise, false.
Implements
Remarks
This member is an explicit interface member implementation. It can be used only when the Tuple<T1, T2> instance is cast to an IStructuralEquatable interface.
The IStructuralEquatable.Equals implementation is called only if other is not nulla null reference (Nothing in Visual Basic), and if it can be successfully cast (in C#) or converted (in Visual Basic) to a Tuple<T1, T2> object whose components are of the same types as the current instance. The IStructuralEquatable.Equals method first passes the Item1 values of the Tuple<T1, T2> objects to be compared to the IEqualityComparer.Equals implementation. If this method call returns true, the method is called again and passed the Item2 values of the two Tuple<T1, T2> objects.
Examples
The following example defines an Item2Comparer class that implements the IEqualityComparer interface and changes the way in which Tuple<T1, T2> objects are evaluated for equality. The method always returns true when it is passed the Item1 property values of two Tuple<T1, T2> objects, and it calls the IStructuralEquatable.Equals method to evaluate their Item2 property values. As a result, the method tests for equality based only on the value of the Item2 property. The output illustrates the result for a data set of Tuple<T1, T2> objects that record the names of runners and the distances that they ran.
Imports System.Collections
Public Class Item2Comparer(Of T1, T2) : Implements IEqualityComparer
Public Overloads Function Equals(ByVal x As Object, ByVal y As Object) As Boolean _
Implements IEqualityComparer.Equals
' Return true for all values of Item1.
If TypeOf x Is T1 Then
Return True
Else
Return x.Equals(y)
End If
End Function
Public Overloads Function GetHashCode(ByVal obj As Object) As Integer _
Implements IEqualityComparer.GetHashCode
If TypeOf obj Is T1 Then
Return CType(obj, T1).GetHashCode()
Else
Return CType(obj, T2).GetHashCode()
End If
End Function
End Class
Module Example
Public Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock)
Dim distancesWalked() As Tuple(Of String, Double) = { _
Tuple.Create("Jan", Double.NaN), _
Tuple.Create("Joe", Double.NaN), _
Tuple.Create("Adam", 1.36), _
Tuple.Create("Selena", 2.01), _
Tuple.Create("Jake", 1.36) }
For ctr As Integer = 0 To distancesWalked.Length - 1
Dim distanceWalked As Tuple(Of String, Double) = distancesWalked(ctr)
For ctr2 As Integer = ctr + 1 To distancesWalked.Length - 1
outputBlock.Text += String.Format("{0} = {1}: {2}", distanceWalked, _
distancesWalked(ctr2), _
DirectCast(distanceWalked, IStructuralEquatable).Equals(distancesWalked(ctr2), _
new Item2Comparer(Of String, Double))) + vbCrLf
Next
outputBlock.Text &= vbCrLf
Next
End Sub
End Module
' The example displays the following output:
' (Jan, NaN) = (Joe, NaN): True
' (Jan, NaN) = (Adam, 1.36): False
' (Jan, NaN) = (Selena, 2.01): False
' (Jan, NaN) = (Jake, 1.36): False
'
' (Joe, NaN) = (Adam, 1.36): False
' (Joe, NaN) = (Selena, 2.01): False
' (Joe, NaN) = (Jake, 1.36): False
'
' (Adam, 1.36) = (Selena, 2.01): False
' (Adam, 1.36) = (Jake, 1.36): True
'
' (Selena, 2.01) = (Jake, 1.36): False
using System;
using System.Collections;
public class Item2Comparer<T1, T2> : IEqualityComparer
{
new public bool Equals(object x, object y)
{
// Return true for all values of Item1.
if (x is T1)
//if (typeof(x) is string)
return true;
else
return x.Equals(y);
}
public int GetHashCode(object obj)
{
if (obj is T1)
return ((T1)obj).GetHashCode();
else
return ((T2)obj).GetHashCode();
}
}
public class Example
{
public static void Demo(System.Windows.Controls.TextBlock outputBlock)
{
Tuple<string, double>[] distancesWalked = {
Tuple.Create("Jan", Double.NaN),
Tuple.Create("Joe", Double.NaN),
Tuple.Create("Adam", 1.36),
Tuple.Create("Selena", 2.01),
Tuple.Create("Jake", 1.36) };
for (int ctr = 0; ctr < distancesWalked.Length; ctr++)
{
Tuple<string, double> distanceWalked = distancesWalked[ctr];
for (int ctr2 = ctr + 1; ctr2 < distancesWalked.Length; ctr2++)
{
outputBlock.Text += String.Format("{0} = {1}: {2}", distanceWalked,
distancesWalked[ctr2],
((IStructuralEquatable)distanceWalked).Equals(distancesWalked[ctr2],
new Item2Comparer<string, double>())) + "\n";
}
outputBlock.Text += "\n";
}
}
}
// The example displays the following output:
// (Jan, NaN) = (Joe, NaN): True
// (Jan, NaN) = (Adam, 1.36): False
// (Jan, NaN) = (Selena, 2.01): False
// (Jan, NaN) = (Jake, 1.36): False
//
// (Joe, NaN) = (Adam, 1.36): False
// (Joe, NaN) = (Selena, 2.01): False
// (Joe, NaN) = (Jake, 1.36): False
//
// (Adam, 1.36) = (Selena, 2.01): False
// (Adam, 1.36) = (Jake, 1.36): True
//
// (Selena, 2.01) = (Jake, 1.36): False
Version Information
Silverlight
Supported in: 5, 4
Platforms
For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.