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Option Explicit On
Option Strict On
Imports System.Data
Imports System.data.SqlTypes
Module Module1
Sub Main()
CompareNulls()
Console.ReadLine()
End Sub
' <Snippet1>
Private Sub CompareNulls()
' Create two new null strings.
Dim a As New SqlString
Dim b As New SqlString
' Compare nulls using static/shared SqlString.Equals.
Console.WriteLine("SqlString.Equals shared/static method:")
Console.WriteLine(" Two nulls={0}", SqlStringEquals(a, b))
' Compare nulls using instance method String.Equals.
Console.WriteLine()
Console.WriteLine("String.Equals instance method:")
Console.WriteLine(" Two nulls={0}", StringEquals(a, b))
' Make them empty strings.
a = ""
b = ""
' When comparing two empty strings (""), both the shared/static and
' the instance Equals methods evaluate to true.
Console.WriteLine()
Console.WriteLine("SqlString.Equals shared/static method:")
Console.WriteLine(" Two empty strings={0}", SqlStringEquals(a, b))
Console.WriteLine()
Console.WriteLine("String.Equals instance method:")
Console.WriteLine(" Two empty strings={0}", StringEquals(a, b))
End Sub
Private Function SqlStringEquals(ByVal string1 As SqlString, _
ByVal string2 As SqlString) As String
' SqlString.Equals uses database semantics for evaluating nulls.
Dim returnValue As String = SqlString.Equals(string1, string2).ToString()
Return returnValue
End Function
Private Function StringEquals(ByVal string1 As SqlString, _
ByVal string2 As SqlString) As String
' String.Equals uses CLR type semantics for evaluating nulls.
Dim returnValue As String = string1.Equals(string2).ToString()
Return returnValue
End Function
' </Snippet1>
End Module