Imports System
Imports System.Collections.Generic
Public Class LetterComparer
Implements IComparer(Of String)
Public Function Compare(ByVal x As String,ByVal y As String) As Integer _
Implements IComparer(Of String).Compare
If x Is Nothing Then
If y Is Nothing Then
Return 0
Else
Return -1
End If
Else
If y Is Nothing Then
Return 1
Else
Dim retval As Integer = x.Length.CompareTo(y.Length)
If retval <> 0 Then
Return retval
Else
Return x.CompareTo(y)
End If
End If
End If
End Function
End Class
Public Class Example
Public Shared Sub Main()
Dim letters As New List(Of String)
letters.Add("A")
letters.Add("B")
letters.Add("C")
letters.Add("D")
Display(letters)
Dim dc As New LetterComparer
letters.Sort(dc)
Display(letters)
SearchAndInsert(letters, "E", dc)
Display(letters)
SearchAndInsert(letters, Nothing, dc)
Display(letters)
End Sub
Private Shared Sub SearchAndInsert(ByVal lis As List(Of String),ByVal insert As String, ByVal dc As LetterComparer)
Dim index As Integer = lis.BinarySearch(insert, dc)
If index < 0 Then
index = index Xor -1
lis.Insert(index, insert)
End If
End Sub
Private Shared Sub Display(ByVal lis As List(Of String))
Console.WriteLine()
For Each s As String In lis
Console.WriteLine(s)
Next
End Sub
End Class