Can''t update smalldatetime field

I have a table with the field end_date which is defined as a smalldatetime.

I have been unable to update this field using the SqlCommand object.

In my windows form I have a DateTime Picker and I am trying to get it's value into the db with no success.

I have tried

command.Parameters.Add ("@.end_date",SqlDbType.DateTime);

command.Parameters["@.end_date"].Value = dtpEndDate.Value;

I have also tried variations of

command.Parameters.AddWithValue ("@.end_date",dtpEndDate.Value);

Please assist if you can.

although I don't believe this is the best way, but it's working.

command.Parameters.AddWithValue("@.end_date", dtpEndDate.Value.ToShortDateString());