The GridView FindControl Mystery RSS

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  artvindustri...

  Member

  14 Points

  52 Posts

  The GridView FindControl Mystery

  Feb 02, 2013 12:10 AM|LINK

  Hello, 

  Its the one issue that keeps coming up. My current Holy Grail of pain. Why won't this simply work?

  protected void lbAll_Click(object sender, EventArgs e)
      {
          CheckBox chkbx = ((CheckBox)FindControl("CheckBox1"));
          GridView grd1 = ((GridView)FindControl("GridView1"));
  
          foreach (GridViewRow gvrow in GridView1.Rows)
          {
  
              if (!chkbx.Checked)
              {
  
                  chkbx.Checked = true;
  
              }
  
          }
      }

  It throws an "Object Reference not set to an instance of an Object" error. 

  This should simply iterate through the rows and check all the unchecked boxes.  Grrr.

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  oned_gk

  All-Star

  31373 Points

  6412 Posts

  Re: The GridView FindControl Mystery

  Feb 02, 2013 12:37 AM|LINK

  Can you explaint whre you place the cb?

  foreach (GridViewRow gvrow in GridView1.Rows)
          {
              CheckBox chkbx = ((CheckBox)gvrrow.FindControl("CheckBox1"));
  
              if (!chkbx.Checked)
              {
  
                  chkbx.Checked = true;
  
              }
  
          }

  
  do you mean?

  GridView grd1 = ((GridView)Page.FindControl("GridView1"));

  
  
  

  Programming to simplify, dont look for hard way
  • Edited by oned_gk on Feb 02, 2013 12:39 AM
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  artvindustri...

  Member

  14 Points

  52 Posts

  Re: The GridView FindControl Mystery

  Feb 02, 2013 12:45 AM|LINK

  Sure thing!

  <div>
  
       <asp:GridView ID="GridView1" runat="server"
                  AutoGenerateColumns="False"
                  GridLines="Both"
                  CssClass="mGrid"
                  PagerStyle-CssClass="pgr"
                  AlternatingRowStyle-CssClass="alt">
                  <AlternatingRowStyle CssClass="alt"></AlternatingRowStyle>
  
                 <Columns>
                      <asp:TemplateField HeaderText="Approve?">
                          <ItemTemplate>
                              <asp:CheckBox ID="CheckBox1" runat="server" text="Approve"/><br />
                          </ItemTemplate>
                      </asp:TemplateField>
                 
  
                </Columns>
                  <PagerStyle CssClass="pgr"></PagerStyle>
        </asp:GridView>
  </div>

  
  
  

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  artvindustri...

  Member

  14 Points

  52 Posts

  Re: The GridView FindControl Mystery

  Feb 02, 2013 01:55 AM|LINK

  Found the problem!

  First stating the problem. This will return all checkboxes as "Its not checked"

  foreach (GridViewRow gr in GridView1.Rows)
          {
              CheckBox cb = (CheckBox)gr.Cells[0].FindControl("CheckBox1");
              if (!cb.Checked)
              {
                  Response.Write("Its not checked");
  
              }
  
              else
              {
                  if (cb.Checked)
                  {
  
                      Response.Write("Its Checked");
                  }
              }
          }

  
  The solution is the .IsPostBack method:

  protected void Page_Load(object sender, EventArgs e)
      {
  
  
          if (!Page.IsPostBack)
          {
              GridView1.DataSource = result;
              GridView1.DataBind();
          }
         
  
      }

  
  The page load rebinds your gridview so the data doesn't stick. I've slain my White Buffalo. lol 

  • Marked as answer by artvindustries on Feb 02, 2013 01:55 AM