Delete DataTable Row Error: Collection was modified enumeration operation might not execute

row deleting from gridview error is coming 

Collection was modified enumeration operation might not execute.

        private void insertintodisgrid()
        {
            DataTable dtp = ViewState["dtp"] as DataTable;
            for (int i = dtp.Rows.Count - 1; i >= 0; i--)
            {
                DataRow dr = dtp.Rows[i];
                if (dr["Prdno"].ToString() == txtno.Text)
                {
                    dr.Delete();
                    Bind();
                }

                insertintopacktxt();
            }
        }