how to make event for button in gridview asp.net vb language?

Question

I have error when i try to click button in gridview that will update selected row

Code and the error in the image

 Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load



    If Not Page.IsPostBack Then
        Try
            Dim con As New SqlConnection
            Dim cmd As New SqlCommand
            Dim dt As New DataTable()

            con.ConnectionString = "Data Source=DESKTOP-L7LKJH5;Initial Catalog=logicist;Integrated Security=True"
            con.Open()

            cmd.CommandText = "select * from dalabaad where Status= @Status"
            cmd.Parameters.AddWithValue("@Status", "Pending".ToString)
            cmd.Connection = con

            Datagrid1.DataSource = cmd.ExecuteReader
            Datagrid1.DataBind()
        Catch ex As Exception
            MsgBox(ex.Message)
        End Try
    End If

    depart()
End Sub

Protected Sub Datagrid1_click(sender As Object, e As GridViewCommandEventArgs)
    ' Update button
    If (e.CommandName = "Select") Then
        Try
            Con.ConnectionString = "Data Source=DESKTOP-L7LKJH5;Initial Catalog=logicist;Integrated Security=True"
            Dim sqlText = "UPDATE dalabaad SET Status = @Status WHERE Invoice_No = '" + Datagrid1.SelectedIndex + "'"
            Using cnConnect = New SqlConnection(Con.ConnectionString)
                Using cm = New SqlCommand(sqlText, cnConnect)
                    cnConnect.Open()
                    cm.Parameters.Add("@Status", SqlDbType.NVarChar).Value = "Approved".ToString

                    cm.ExecuteNonQuery()
                    MsgBox("Updated")
                End Using
            End Using
        Catch ex As Exception
            MsgBox(ex.Message)
        End Try
    End If


End Sub

Asp.net vb code

        <asp:GridView ID="Datagrid1" runat="server" AutoGenerateColumns="False" Width="860px" OnRowCommand="Datagrid1_click" >
<Columns>
    <asp:BoundField DataField="RefNo" HeaderText="RefNo" ReadOnly="True" />
    <asp:BoundField DataField="Invoice_No" HeaderText="Invoice_No" />
    <asp:BoundField DataField="Item_Name" HeaderText="ITem Name" />
    <asp:BoundField DataField="Quantity" HeaderText="Quantity" />
    <asp:BoundField DataField="Department" HeaderText="Department" />
    <asp:BoundField DataField="ReceiverName" HeaderText="Receiver Name" />
    <asp:BoundField DataField="Date" HeaderText="Date" />
    <asp:BoundField DataField="Approval_By" HeaderText="Approval_By" />
    <asp:BoundField DataField="Status" HeaderText="Status" />
    <asp:TemplateField>
        <ItemTemplate>
            <asp:Button runat="server"  Text="Button" CommandName="Select"  ></asp:Button>
        </ItemTemplate>
    </asp:TemplateField>

</Columns>

</asp:GridView>

HTML Code for Gridview

Object reference not set to an instance of an object.

Error message when i click the button in Gridview

I have tried to change places several times and it didn't work for me

Answer 1

It's best to drop in a plain asp.net button into that gridview.

So, this:

       <asp:Button id="cmdmyupdate" runat="server"  
            Text="Status Update" 
            OnClick="cmdmyupdate_Click"
        >
        </asp:Button>

So, let vs create the click event (like you do for ANY plain button, right?).

So, it looks like this while typing: (you need/want to use/let intel-sense create the button event for code behind).

OK, so now if we flip to code behind, we have our button click.

So, now your code can be this:

So, we need to get/grab the invoice number from that row.

We have to use .Cells() collection (starts at zero, so invoice num is 2nd one, or "1").

Protected Sub cmdmyupdate_Click(sender As Object, e As EventArgs)


    Dim btn As Button = sender
    Dim gvRow As GridViewRow = btn.NamingContainer
    Dim sInvoice As String = gvRow.Cells(1).Text

    Dim scon As String =
       "Data Source=DESKTOP-L7LKJH5;Initial Catalog=logicist;Integrated Security=True"

    Dim sqlText As String =
       "UPDATE dalabaad SET Status = @Status WHERE Invoice_No = @InvoiceNum"
    Using cnConnect = New SqlConnection(scon)
        Using cm = New SqlCommand(sqlText, cnConnect)
            cnConnect.Open()
            cm.Parameters.Add("@Status", SqlDbType.NVarChar).Value = "Approved"
            cm.Parameters.Add("@InvoiceNum", SqlDbType.NVarChar).Value = sInvoice
            cm.ExecuteNonQuery()
        End Using
    End Using

End Sub