Cannot pull SUM using intscalar

See more:

C#

MySQL

I am attempting to pull a SUM amount from a mySql database, using an intScalar query.

This is the calling code (The DBConnect class connects to the database):

DateTime reportStart = startDate.Date;

DBConnect reportConn = new DBConnect();
MySqlCommand reportQuery = new MySqlCommand();

reportQuery.CommandText = @"SELECT sum(amount) as total
FROM dbo.table
where created <= @startDate";

reportQuery.Parameters.Add("@startDate", MySqlDbType.Date).Value = reportStart.Date;
int xOutstanding = reportConn.intScalar(reportQuery);
lblRewardsDateX.Text = xOutstanding.ToString();

And the intScalar:

public int intScalar(MySqlCommand cmd)
      {
          int returnInt = -1;

          try
          {
              this.OpenConnection();
              cmd.Connection = connection;

              //ExecuteScalar will return one value
              returnInt = Convert.ToInt32(cmd.ExecuteScalar());
              this.CloseConnection();
              return returnInt;

          }
          catch (Exception ex)
          {
              MessageBox.Show(ex.Message);
          }
          return returnInt;
      }

However, it is throwing an exception:

Object cannot be cast from DBNull to other types.

I have double-checked the parameter being passed to the command, and it is not null. So why is it throwing the exception?

What I have tried:

Analyzed the parameter to ensure it is not a null value