show selected checkbox value in text box in gridview

//write code on button click
for (int i = 0; i < GridView1.Rows.Count; i++)
{
CheckBox c = (CheckBox)GridView1.Rows[i].FindControl("CheckBox1");
if (c.Checked)
{
string abc = "select * from candidate where c_id='" + GridView1.Rows[i].Cells[1].Text + "'";
SqlDataAdapter adp1 = new SqlDataAdapter(abc, con);
DataSet ds1 = new DataSet();
adp1.Fill(ds1, "aaa");
TextBox2.Text = ds1.Tables[0].Rows[0][1].ToString();
TextBox3.Text = ds1.Tables[0].Rows[0][2].ToString();
}
}