How to Access Programmatically Added checkbox

Question

I am developing an application in which i needed the to add filter. for that am adding checkbox programmatically because the filtering option are not predefine it depends on the value in the table to i add the checkbox as fallow

public void addCusineCheckbox()
{
            DataTable CusineList = Sql.ExecuteSelectCommand("select prod_group_id,Prod_group_name from Master_Prod_Groups");
            for (int i = 0; i < CusineList.Rows.Count; i++)
            {
                CheckBox chkCusine = new CheckBox();
                chkCusine.ID = "chk" + CusineList.Rows[i]["Prod_group_name"].ToString();
                chkCusine.Text = CusineList.Rows[i]["Prod_group_name"].ToString();
                divCusineFilter.Controls.Add(chkCusine);
            }
}

which help user to select the required field(there more other option to select) and then click on apply filter on that am try to access the that added check box as fallow

public string getCusineFilterString()
{

            string CusineID =null;
            DataTable CusineList = Sql.ExecuteSelectCommand("select prod_group_id,Prod_group_name from Master_Prod_Groups");
            for (int i = 0; i < CusineList.Rows.Count; i++)
            {
                CheckBox chk = (CheckBox)Page.FindControl("chk" + CusineList.Rows[i]["Prod_group_name"]);
                if (chk.Checked == true)
                {
                    if (i == 0)
                    {
                        CusineID = CusineList.Rows[i]["prod_group_id"].ToString();
                    }
                    else
                    {
                        CusineID = CusineID + "," + CusineList.Rows[i]["prod_group_id"].ToString();
                    }
                }
            }
            return CusineID;
}

but it gives the error that object not set to an instance.

i am not getting any idea to access to the checkbox.

Im going to guess that chk is null so add to your if which should look like `if (chk != null && chk.Checked == true)` — Ashley Medway, Dec 17 '13 at 08:51
sir i have add the check box on page load event. and on button click event am try to check all the check box to form the filtering constraint . for that am try to access the programmatically added check box by using findcontrol and form the same id as i assign it while adding but it doesnot getting — Rhushikesh, Dec 17 '13 at 08:53

score 3 · Accepted Answer · answered Dec 17 '13 at 08:56

There are certain limitations:

You cannot access any controls in ASP.net which are not added before or on Init. So you can add the controls on Page OnInit, and then it will be accessible. But you have to be careful in adding the controls, so that they are added at right place and not duplicated.
You should not write

CheckBox chk = (CheckBox)Page.FindControl("chk");

instead write

var chkControl = Page.FindControl("chk");
if(chkControl != null /*&& check type*/) {
  CheckBox chk = (CheckBox)chkControl;
// and do something
}

It will be better if you use CheckBoxList Control at design time and change the binding values to populate different check boxes at runtime
Create check box(s) at design time and show hide based on user action.

Hope it helps

you were first, i just write code like this. I think is what he needed — Sebastian 506563, Dec 17 '13 at 08:58

score 0 · Answer 2 · edited May 23 '17 at 10:25

You can get the values using Request.Forms collection. It keeps the values of every control which is on the form. But it works on name rather than ID.

Get dynamic control (unique ID) on postback

The better approach is use empty CheckBoxList and add item at run-time.

Here is a link which has discussion on CheckBoxList
How can I get the CheckBoxList selected values, what I have doesn't seem to work C#.NET/VisualWebPart

Example

Create an empty

<asp:CheckBoxList ID="ChkBox1" runat="server"></asp:CheckBoxList>

And add items at runtime

 ChkBox1.Items.Add(new ListItem("Item 1", "Item1"));

And you can get data by using foreach loop as follow

  // Loop through each item.
    foreach (ListItem item in ChkBox1.Items)
    {
        if (item.Selected)
        {
            // If the item is selected, add the value to the list.

        }
        else
        {
            // Item is not selected, do something else.
        }
    }

score 0 · Answer 3 · answered Dec 17 '13 at 09:29

0

You can add your checkboxes in Page_Load. I think the problem is in using Page.FindControl. Use divCusineFilter.FindControl rather than Page.FindControl and make sure that you add your checkboxes to page in postback too.

answered Dec 17 '13 at 09:29

Alborz

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How to Access Programmatically Added checkbox

3 Answers3

Example