ping in vb error

[markhorgan1]

i have the following code but when i select button1 i get the following error: Null Reference Exception was unhandled-object reference not set to an instance of an object. - any idea's how to fix it ??
*i have underlined the line of code that is highligted when the error occurs

Imports System.Data


Public Class Form1

    Dim Ping As Net.NetworkInformation.Ping
    Dim pReply As Net.NetworkInformation.PingReply
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

    End Sub

    Public Sub btnLoad_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnLoad.Click
        Dim ds As New DataSet
        Dim da As OleDb.OleDbDataAdapter
        Dim sql As String

      


        Dim con As New OleDb.OleDbConnection
        con.ConnectionString = "PROVIDER=Microsoft.Jet.OLEDB.4.0;Data Source = C:\Documents and Settings\mhorgan\Desktop\VBtest.mdb"
        con.Open()

        sql = "SELECT * FROM tblone"
        da = New OleDb.OleDbDataAdapter(sql, con)
        da.Fill(ds, "monitor")



    End Sub

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Try
            Ping = New Net.NetworkInformation.Ping

            pReply = Ping.Send("143.239.167.240")

            Label1.Text = pReply.Status.ToString




            If pReply.Status = Net.NetworkInformation.IPStatus.Success Then
                Dim ds As New DataSet
                Dim da As OleDb.OleDbDataAdapter
                Dim sql As String






                Dim con As New OleDb.OleDbConnection
                con.ConnectionString = "PROVIDER=Microsoft.Jet.OLEDB.4.0;Data Source = C:\Documents and Settings\mhorgan\Desktop\VBtest.mdb"
                con.Open()

                sql = "SELECT * FROM tblone"
                da = New OleDb.OleDbDataAdapter(sql, con)
                da.Fill(ds, "monitor")


                Dim cb As New OleDb.OleDbCommandBuilder(da)

                ds.Tables("monitor").Rows(0).Item(1) = Label1.Text

                da.Update(ds, "monitor")







            Else
                Label1.BackColor = Color.Red
            End If

        Catch ex As Exception

            MessageBox.Show(ex.InnerException.Message)
        End Try
    End Sub

    
    Private Sub btnExit_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnExit.Click
        Dim con As New OleDb.OleDbConnection
        con.ConnectionString = "PROVIDER=Microsoft.Jet.OLEDB.4.0;Data Source = C:\Documents and Settings\mhorgan\Desktop\VBtest.mdb"
        con.Close()
        End

    End Sub
End Class

[jmcilhinney]

You are assuming that the exception that is thrown initially has an inner exception. Apparently it doesn't. While debugging you should simply do this:

MessageBox.Show(ex.ToString())

and you'll get basically all available information.

[markhorgan1]

works now ! thanks !

[markhorgan1]

i have tried altering the code and am now gettin another error.instead of having the ip address hardcoded in to the code i want it to be read in from the access db but im now getting this error:System.nullreferenceExceptionbject reference not set to an instance of an object at...button1.click event args e
i have underlined the piece of code i tried to change

Imports System.Data


Public Class Form1

    Dim Ping As Net.NetworkInformation.Ping
    Dim pReply As Net.NetworkInformation.PingReply
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

    End Sub

   

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

        Dim ds As New DataSet
        Dim da As OleDb.OleDbDataAdapter
        Dim sql As String
        Dim con As New OleDb.OleDbConnection


        Try
            Ping = New Net.NetworkInformation.Ping

            pReply = Ping.Send(ds.Tables("monitor").Rows(0).Item(0))

            Label1.Text = pReply.Status.ToString




            If pReply.Status = Net.NetworkInformation.IPStatus.Success Then


                con.ConnectionString = "PROVIDER=Microsoft.Jet.OLEDB.4.0;Data Source = C:\Documents and Settings\mhorgan\Desktop\VBtest.mdb"
                con.Open()

                sql = "SELECT * FROM tblone"
                da = New OleDb.OleDbDataAdapter(sql, con)
                da.Fill(ds, "monitor")


                Dim cb As New OleDb.OleDbCommandBuilder(da)

                ds.Tables("monitor").Rows(0).Item(1) = Label1.Text

                da.Update(ds, "monitor")







            Else
                Label1.BackColor = Color.Red
            End If

        Catch ex As Exception

            MessageBox.Show(ex.ToString())

        End Try
    End Sub


    Private Sub btnExit_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnExit.Click
        Dim con As New OleDb.OleDbConnection
        con.ConnectionString = "PROVIDER=Microsoft.Jet.OLEDB.4.0;Data Source = C:\Documents and Settings\mhorgan\Desktop\VBtest.mdb"
        con.Close()
        End

    End Sub
End Class

[jmcilhinney]

It looks like you're trying to read data from the DataTable before you even populate it.