Dim SQLResult As Object
        Dim connStr As String = "Provider=Microsoft.Jet.OLEDB.4.0; Data" & _
          "Source=c:\test.mdb"
        Dim dbConnection As OleDbConnection = New OleDbConnection(connStr)
        Dim SQL As New OleDbCommand
 
        dbConnection.Open()
        SQL.Connection = dbConnection
 
        SQL.CommandText = "SELECT COUNT([id]) FROM Tabelle "  
 
if Varname = "" then
        SQL.CommandText = SQL.CommandText & "WHERE ([Name] IS NULL) "        
else
        SQL.CommandText = SQL.CommandText & "WHERE ([Name] = '" & VarName & "')        
End If
 
        SQLResult = SQL.ExecuteScalar
 
        MsgBox(SQLResult.ToString)

Zitat:

2. NIEMALS, ich wiederhole NIEMALS die parameter einer Sql Abfrage in den Sql String friemeln. Benutze die Parameters Collection des Commands.