insertind date problem

protected void Button2_Click(object sender, EventArgs e)

{

 DateTime? joingdate;

 joingdate = DateTime.ParseExact(joing.Text, "dd/MM/yyyy",null);

SqlCommand cmd = new SqlCommand("insert into acmaster(Name,Addr1,Mobile,Emailid,Panno,Nominee,Relation,Sponcerid,Sponcustno,Itemcode,Itemprice,commission,joing)values('" + customer.Text + "','" + adderss.Text + "','" + mobile.Text + "','" + emailid.Text + "','" + panno.Text + "','" + nomineen.Text + "','" + nomineer.Text + "','" + rankcode.Text + "','" + custno.Text + "','" + productid.Text + "','" + prize.Text + "','"+commission.Text+"'.'"+d+"')", con);

cmd.CommandType = CommandType.Text;

try

{

con.Open();

cmd.ExecuteNonQuery();

// Label25.Text = "data Inserted";

Response.Write("");

con.Close();

clearfield();

}

catch (Exception ex)

{

Label25.Text = ex.Message;

}

}