displaying value twice

[krisssgopi]

Hi Team,

below coding is working fine. it was displaying the value in the list box once i press the button1. But when i click the button1 once more the result was getting twice. i.e., previous value is displayed plus same value was repeated twice. overall three times. please help me in this regard.

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Try
 
            con.Open()
            MsgBox("con opened..")
            cmd.CommandType = CommandType.Text
            cmd.CommandText = "select * from student"
            da = New SqlDataAdapter(cmd.CommandText, con)
            da.Fill(ds)
 
            Dim i, maxcount As Integer
            maxcount = ds.Tables(0).Rows.Count
 
            Dim a(maxcount - 1) As String
            For i = 0 To maxcount - 1
                a(i) = ds.Tables(0).Rows(i).Item(1)
            Next
            For i = 0 To maxcount - 1
                ListBox1.Items.Add(a(i))
            Next
        Catch ex As Exception
            MsgBox(ex.Message.ToString)
        End Try
        con.Close()
        MsgBox("con closed..")
    End Sub

[Monomachus]

@krisssgopi
Hi, please add tags to your question.
Now on the topic I can see why these values could be doubled.

Because you don't clear you old values from your listbox before inserting the new ones:

Listbox1.Items.Clear();
 

But I don't know how to explain that it was repeated two times (overall three).

Please try to clear the items and see what happens next.

P.S. Please use code button or tags to insert the code. Thanks in advance

[krisssgopi]

@Monomachus
Hi Mono really thanks for your reply... one more think ow to develop my developing skills please advise me in this regard. thanks in advance..