IComparer.Compare Method
Compares two objects and returns a value indicating whether one is less than, equal to, or greater than the other.
Namespace: System.Collections
Assembly: mscorlib (in mscorlib.dll)
Parameters
- x
- Type: System.Object
The first object to compare.
- y
- Type: System.Object
The second object to compare.
Return Value
Type: System.Int32A signed integer that indicates the relative values of x and y, as shown in the following table.
Value | Meaning |
|---|---|
Less than zero | x is less than y. |
Zero | x equals y. |
Greater than zero | x is greater than y. |
| Exception | Condition |
|---|---|
| ArgumentException | Neither x nor y implements the IComparable interface. -or- x and y are of different types and neither one can handle comparisons with the other. |
The preferred implementation is to use the CompareTo method of one of the parameters.
Comparing Nothing with any type is allowed and does not generate an exception when using IComparable. When sorting, Nothing is considered to be less than any other object.
The following code example demonstrates the use of the IComparer interface to sort an ArrayList object. In this example, the IComparer interface is implemented using the CaseInsensitiveComparer class to reverse the order of the contents of the ArrayList.
Imports System Imports System.Collections Imports Microsoft.VisualBasic Public Class SamplesArrayList Public Class myReverserClass Implements IComparer ' Calls CaseInsensitiveComparer.Compare with the parameters reversed. Public Function Compare( ByVal x As Object, ByVal y As Object) As Integer _ Implements IComparer.Compare Return New CaseInsensitiveComparer().Compare(y, x) End Function 'IComparer.Compare End Class 'myReverserClass Public Shared Sub Main() ' Creates and initializes a new ArrayList. Dim myAL As New ArrayList() myAL.Add("The") myAL.Add("quick") myAL.Add("brown") myAL.Add("fox") myAL.Add("jumps") myAL.Add("over") myAL.Add("the") myAL.Add("lazy") myAL.Add("dog") ' Displays the values of the ArrayList. Console.WriteLine("The ArrayList initially contains the following values:") PrintIndexAndValues(myAL) ' Sorts the values of the ArrayList using the default comparer. myAL.Sort() Console.WriteLine("After sorting with the default comparer:") PrintIndexAndValues(myAL) ' Sorts the values of the ArrayList using the reverse case-insensitive comparer. Dim myComparer = New myReverserClass() myAL.Sort(myComparer) Console.WriteLine("After sorting with the reverse case-insensitive comparer:") PrintIndexAndValues(myAL) End Sub 'Main Public Shared Sub PrintIndexAndValues(myList As IEnumerable) Dim i As Integer = 0 Dim obj As [Object] For Each obj In myList Console.WriteLine(vbTab + "[{0}]:" + vbTab + "{1}", i, obj) i = i + 1 Next obj Console.WriteLine() End Sub 'PrintIndexAndValues End Class 'SamplesArrayList 'This code produces the following output. 'The ArrayList initially contains the following values: ' [0]: The ' [1]: quick ' [2]: brown ' [3]: fox ' [4]: jumps ' [5]: over ' [6]: the ' [7]: lazy ' [8]: dog ' 'After sorting with the default comparer: ' [0]: brown ' [1]: dog ' [2]: fox ' [3]: jumps ' [4]: lazy ' [5]: over ' [6]: quick ' [7]: the ' [8]: The ' 'After sorting with the reverse case-insensitive comparer: ' [0]: the ' [1]: The ' [2]: quick ' [3]: over ' [4]: lazy ' [5]: jumps ' [6]: fox ' [7]: dog ' [8]: brown
Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.
