Unable to selected checkbox

Collapse
X
Collapse
 
  • Page of 1
  • Time
  • Show
Clear All
new posts
Previous template Next
  • Wally McKean
    New Member
    • Dec 2011
    • 3
    #1

    Unable to selected checkbox

    I am unable to update table when the users clicks on the register button. My code is listed below.

    vb:
    Code:
    Dim retstruct As RegisterCourseInfo
        Dim uN As String


        For Each row As GridViewRow In GridView1.Rows
            Dim cb As CheckBox = CType(GridView1.FindControl("ChkSelect"), CheckBox)

            If cb IsNot Nothing AndAlso cb.Checked Then

                uN = GridView1.DataKeys(row.RowIndex).Value
                retstruct = RegisterCourseIndividual(Request.QueryString("CourseID"), Request.QueryString("SessionID"), uN, False)
                cb.Checked = False

            End If
        Next
    Code:
    <asp:TemplateField InsertVisible="False">
            <ItemTemplate>
                <asp:CheckBox ID="ChkSelector" ViewStateMode="disabled" Checked="false" runat="server" />
            </ItemTemplate>
        </asp:TemplateField>
    Would anyone have any ideas of why I am not getting the correct results?

    Thank you in advance for looking.
    Last edited by Frinavale; Dec 16 '11, 02:54 PM. Reason: Added code tags
    Tags: None
    • Frinavale
      Recognized Expert Expert
      • Oct 2006
      • 9749
      #2
      There are 2 reasons why you aren't retrieving the CheckBox.
      First of all, the CheckBox exists each Row in the the GridView.
      So, the following:
      Code:
       Dim cb As CheckBox = CType(GridView1.FindControl("ChkSelect"), CheckBox)
      Should be:
      Code:
       Dim cb As CheckBox = CType(row.FindControl("ChkSelect"), CheckBox)
      The second problem is that you don't have a CheckBox with the ID "ChkSelect" in your row....you have a CheckBox with the ID "ChkSelecto r".

      So, the following will fix the problem:
      Code:
       Dim cb As CheckBox = CType(row.FindControl("ChkSelector"), CheckBox)

      Here's the example that I used to debug your problem.
      (ASP.NET code)
      Code:
      <%@ Page Language="vb" AutoEventWireup="false" CodeBehind="WebForm1.aspx.vb" Inherits="WebApplication1.WebForm1" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title></title>
</head>
<body>
    <form id="form1" runat="server">
    <asp:GridView ID="GridView1" runat="server">
        <Columns>
            <asp:TemplateField InsertVisible="False">
                <ItemTemplate>
                    <asp:CheckBox ID="ChkSelector" ViewStateMode="disabled" Checked="false" runat="server" />
                </ItemTemplate>
            </asp:TemplateField>
        </Columns>
    </asp:GridView>
    <asp:Button runat="server" ID="showCheckedRows" Text="show checked rows" />
    <br />
    <asp:Label runat="server" ID="checkedRows" />
    </form>
</body>
</html>
      (VB.NET code)
      Code:
      Public Class WebForm1
    Inherits System.Web.UI.Page
    Private _dt As DataTable
    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
        If Session("_dt") Is Nothing Then
            RetrieveDataSource()
        Else
            _dt = DirectCast(Session("_dt"), DataTable)
        End If
    End Sub
    Private Sub WebForm1_PreRender(sender As Object, e As System.EventArgs) Handles Me.PreRender
        GridView1.DataSource = _dt
        GridView1.DataBind()
    End Sub

    Private Sub showCheckedRows_Click(sender As Object, e As System.EventArgs) Handles showCheckedRows.Click
        Dim selectedRowText As New StringBuilder
        Dim index As Integer = 0
        For Each row As GridViewRow In GridView1.Rows
            Dim cb As CheckBox = CType(row.FindControl("ChkSelector"), CheckBox)
            If cb IsNot Nothing AndAlso cb.Checked Then
                selectedRowText.Append("row: ")
                selectedRowText.Append(index.ToString)
                selectedRowText.Append("<br />")
            End If
            index += 1
        Next
        checkedRows.Text = selectedRowText.ToString
    End Sub

    Private Sub RetrieveDataSource()
        _dt = New DataTable
        _dt.Columns.Add("ID", GetType(Integer))
        _dt.Columns.Add("Name")

        For i As Integer = 1 To 10
            Dim dr As DataRow = _dt.NewRow
            dr("ID") = i
            dr("Name") = "Name " + i.ToString
            _dt.Rows.Add(dr)
        Next
        Session("_dt") = _dt
    End Sub
End Class

        Comment

        • Wally McKean
          New Member
          • Dec 2011
          • 3
          #3
          Thank you for your help. I pasted the incorrect code after looking at your response and I had the correct findcontrol name. I have entered what you have supplied and when I run the page it bypasses the following lines:
          Code:
           If cb IsNot Nothing AndAlso cb.Checked Then
   selectedRowText.Append("row: ")
   selectedRowText.Append(index.ToString)
   selectedRowText.Append("<br />")
 End If
          Would you happen to know what may cause the code to bypass the if statement?

          Thank you again for your advice.
          Last edited by Frinavale; Dec 16 '11, 09:30 PM. Reason: Added code tags.

            Comment

            • Frinavale
              Recognized Expert Expert
              • Oct 2006
              • 9749
              #4
              It will bypass that case if cb is nothing or it's not checked.

              I recommend adding a new WebForm1.aspx to your project.
              Copy the code that I have for the ASP part and paste it into the form. Then copy the VB.NET code into the code behind for the page.

              I've tested it and it works fine.

                Comment

                • Frinavale
                  Recognized Expert Expert
                  • Oct 2006
                  • 9749
                  #5
                  A guess, off the top of my head, would be that you are calling the DataBind method on the GridView in the Page Load event.

                  If you do this, anything that the user provided will be lost because the GridView re-binds to the original data.

                  You should hold off calling the DataBind method until the PreRender event since it occurs after all of the other page events are done.

                  -Frinny

                    Comment

                    • Wally McKean
                      New Member
                      • Dec 2011
                      • 3
                      #6
                      Thank you for your help. I just figured it out. Once I put the checkbox if loop into a if Page.ispostback everything went through and updated as needed. You pointed me in the right direction and I really glad that there are people out there that help us that need it. Thanks again.

                        Comment

                        Previous template Next
                        Working...