ASP.NET

cmd.Parameters.Add("DOB", SqlDbType.SmallDateTime).Value = txtDOB.Text;

cmd.Parameters.Add("DOB", SqlDbType.SmallDateTime).Value =  (string.IsNullOrEmpty( txtDOB.Text)) ? DBNull.Value.ToString() : txtDOB.Text;

public static object GetValueForParameter(string value)
{
  if (!string.IsNullOrWhitespace(value))
    return value;
  return DBNull.Value;
}

public void InsertTableRow()
{
   //here i have inserted a new row into my table..

   //now i will show the updates in a popup modal like so:
   popupModal.Style.Value = "display:block;";
   //watch here, am applying new style for this div on a div-id, which then mean that all your fancy css styles should be appended to your class(e.g. myPopupClass). if u include all your css on your id and u execute the above code to show your modal the css is going to be overwritten....
}

context.Response.Write(
  "<input type=submit name='Lookup'
value='Lookup'></input>");

if(txtBox.Text.Contains("<script")
    //This text contains script.//