Dynamic adding of checkboxes in asp.net using c#?

Question

I am trying to add two sets of checkboxes in my asp.net project. There I am doing this:

on page load:

 public static CheckBox[] chck = new CheckBox[100];
 public static CheckBox[] chckbx = new CheckBox[100];   

and i have a functions:

  public void generatecheckbox1()
{
    for (int i = 0; i < 99; i++)
    {
        chck[i] = new CheckBox();
        chck[i].ID = chck + Convert.ToString(i);
        chck[i].Text = chck + Convert.ToString(i);
        pnlcom1.Controls.Add(chck[i]);
        pnlcom1.Controls.Add(new LiteralControl("<br />"));

        chckbx[i] = new CheckBox();
        chckbx[i].ID = chckbx + Convert.ToString(i);
        chckbx[i].Text = chckbx + Convert.ToString(i);
        pnlcom2.Controls.Add(chckbx[i]);
        pnlcom2.Controls.Add(new LiteralControl("<br />"));
    }
}

and i am calling this function here:

protected void ddluserwebser_SelectedIndexChanged(object sender, EventArgs e)
{
    if (ddluserwebser.SelectedItem.Text == "Custom")
    {
        generatecheckbox1();

    }
}

The problem is i am getting an error page like this:

its saying this:

Multiple controls with the same ID 'System.Web.UI.WebControls.CheckBox[]0' were found. FindControl requires that controls have unique IDs.

But I am assigning different ids.. what should i do?

Answer 1

don't chck here chck[i].ID = chck + Convert.ToString(i); needs to be chck[i].ID = "chck" + Convert.ToString(i);

Answer 2

The problem is that you're creating two checkboxes in one loop iteration with the same id. That's not allowed in ASP.NET when they are in the same NamingContainer(Panel doesn't implement INamingContainer).

So change it to(note the string.Format part):

for (int i = 0; i < 99; i++)
{
    chck[i] = new CheckBox();
    chck[i].ID = string.Format("chk_1_{0}", i);
    chck[i].Text = chck + Convert.ToString(i);
    pnlcom1.Controls.Add(chck[i]);
    pnlcom1.Controls.Add(new LiteralControl("<br />"));

    chckbx[i] = new CheckBox();
    chck[i].ID = string.Format("chk_2_{0}", i);
    chckbx[i].Text = chckbx + Convert.ToString(i);
    pnlcom2.Controls.Add(chckbx[i]);
    pnlcom2.Controls.Add(new LiteralControl("<br />"));
}

You also have used the CheckBox[] to build your ID

chckbx + Convert.ToString(i);

That works seemingly since Type + string = name of the type + string but looks like:

"System.Windows.Forms.CheckBox[]99"

So just use the code above

string.Format("chk_1_{0}", i);