I have to store a ajax calender date into sql column having datatype date.

protected void gvImages_RowUpdating(object sender, GridViewUpdateEventArgs e)
    {
        
        SqlConnection con = new SqlConnection(@"Data Source=.\SQLEXPRESS;AttachDbFilename=D:\site\SamsungClassifieds\App_Data\Dorknozzle.mdf;Integrated Security=True;User Instance=True");
        con.Open();
        AjaxControlToolkit.CalendarExtender date = (AjaxControlToolkit.CalendarExtender)gvImages.Rows[e.RowIndex].FindControl("date3");
        //int userid = Convert.ToInt32(gvImages.DataKeys[e.RowIndex].Values["lbladid"].ToString());
        Label lbladid = (Label)gvImages.Rows[e.RowIndex].FindControl("lbladid");
        TextBox txttitl = (TextBox)gvImages.Rows[e.RowIndex].FindControl("txttitle");
        TextBox txtdesc = (TextBox)gvImages.Rows[e.RowIndex].FindControl("txtdesc");
        Label lblprice = (Label)gvImages.Rows[e.RowIndex].FindControl("lblprice");
        TextBox txtprice = (TextBox)gvImages.Rows[e.RowIndex].FindControl("txtprice");
        TextBox txtdate = (TextBox)gvImages.Rows[e.RowIndex].FindControl("txtdate");
        
   
        
        SqlCommand cmd = new SqlCommand("UPDATE AD_DETAIL SET AD_TITLE ='" + txttitl.Text + "',AD_DESC ='" + txtdesc.Text + "',AD_PRICE ='" + txtprice.Text + "',DATE =' "+ date.SelectedDate.ToString() +" 'WHERE AD_ID = '" + lbladid.Text + "'", con);
        
        //SqlCommand cmd = new SqlCommand("Update AD_DETAIL set AD_TITLE=" + txttitle.Text + "where AD_ID =" + lbladid, con);
        cmd.ExecuteNonQuery();
        gvImages.EditIndex = -1;
        Binddata();
        con.Close();

    }