troubleshooting Question

How to rectify error in Vb.Net Windows form for click on button for db connectivity issues

Avatar of searchsanjaysharma
searchsanjaysharma asked on
Visual Basic.NET
3 Comments1 Solution357 ViewsLast Modified:
There is a textbox txtauin and button btnuin.
The users enters the uin and click on uin and get the details.
But if txtauin is blank and user clicks on btnuin, then the error comes Object reference not set to instance of an object.

Code is here.

    Private Sub btnuin_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnuin.Click
        Try
            If (txtauin.Text.Trim() <> "") Then
                con = New SqlConnection("Data Source=172.16.3.17;Initial Catalog=testadms;User Id=sa;Password=admin#cgc;")
                s = "SELECT isnull(ahstatus,'') from mststudents where uin='" & txtauin.Text.Trim() & "'"

                If (con.State = ConnectionState.Closed) Then
                    con.Open()
                End If
                da = New SqlDataAdapter(s, con)
                dt = New DataTable

                da.Fill(dt)

                If (dt.Rows.Count = 0) Then
                    MessageBox.Show("No Record Found")
                    txtauin.Text = ""
                Else
                    'Timer1_Tick()
                    txtahstatus.Text = dt.Rows(0)(0).ToString()
                                End If
            end if

            Else
                MsgBox("Invalid UIN")
            End If
        Catch ex As Exception
            MsgBox(ex.ToString())
        Finally
            con.Close()
        End Try
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