im sorry but i've tried this code and it gives me the following error

NullReferenceException

"Object reference not set to an instance of an object."

else i added a textbox control to the form and maked equal its text property to the gridview cell text property (fifth cell) but nothing was apperead in the textbox . i didnt understand why

As I stated in my previous post, if you are binding to a control the Text Property of your cell will return and empty string.

I just ran a variation of your code and it seemed to work fine:

foreach (GridViewRow gvr in gv.Rows)
{
            bool isChecked = ((CheckBox)gvr.FindControl("chkSec")).Checked;

            if (isChecked)
            {
                Label lbl = (Label)gvr.FindControl("lblID");
                str.Append(lbl.Text);
            }
}

What triggers your code to be run? Are you making sure to rebind your grid on postbacks?

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thanks a lot ,it runs

For the sake of any other person that might be having the same issue, can you explain how you fixed your issue and what code you used to resolve your problem?

================================================== =========
Read this if you want to know how to get a correct reply for your question:
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================================================== =========
.: Wrox Technical Editor / Author :.
Wrox Books 24 x 7
================================================== =========

i've used this code :

protected void LinkButton1_Click(object sender, EventArgs e)
    {

        StringBuilder str = new StringBuilder();

        for (int i = 0; i < gv.Rows.Count; i++)
        {
            GridViewRow row = gv.Rows[i];
            bool isChecked = ((CheckBox)row.FindControl("chkSec")).Checked;

            if (isChecked)
            {
                str.AppendFormat("<p>{0}) {1}<br/></p>", ((Label)row.FindControl("lblID")).Text,((Label)row .FindControl("lblQID")).Text);
            }
        }
   Response.Write(str.ToString());
}