SQL DataReader missing a row in loop

Question

When running the following code it leaves out one row. When I do a files.Count it says there are 4 rows but there is no data stored for the 4th row. When I run the stored procedure from within SQL Manager it returns all 4 rows and all the data. Any help?

            List<File> files = new List<File>();
            SqlConnection active_connection = new SqlConnection(m_connection_string);
            SqlCommand cmd = new SqlCommand();
            SqlDataReader dr = null;

            try
            {
                active_connection.Open();
                cmd.Connection = active_connection;
                cmd.CommandType = CommandType.StoredProcedure;
                cmd.CommandText = "dalsp_Select_Organization_Files";

                SqlParameter param;

                param = cmd.Parameters.Add("@p_organization_guid", SqlDbType.UniqueIdentifier);
                param.Value = new Guid(organization_guid);

                param = cmd.Parameters.Add("@p_file_type", SqlDbType.NVarChar, 50);
                param.Value = file_type;

                dr = cmd.ExecuteReader(CommandBehavior.CloseConnection);

                if (dr.HasRows)                    
                {                    
                    while (dr.Read())
                    {
                        File file = new File();
                        file.OrganizationGuid = dr["OrganizationGuid"].ToString();
                        file.FileGuid = dr["FileGuid"].ToString();
                        file.FileLocation = dr["FileLocation"].ToString();
                        file.FileName = dr["FileName"].ToString();
                        file.FileType = (FileTypeEnum)Enum.Parse(typeof(FileTypeEnum), dr["FileType"].ToString());
                        file.FileExtension = dr["FileExtension"].ToString();
                        file.FileDescription = dr["FileDescription"].ToString();
                        file.ThumbnailPath = dr["ThumbnailPath"].ToString();
                        files.Add(file);
                    }       
                }
                dr.Close();
                dr = null;

                active_connection.Close();
                cmd = null;

            }
            catch (Exception)
            {
                throw;
            }
            finally
            {
                if (active_connection.State != ConnectionState.Closed)
                {
                    active_connection.Close();
                    active_connection.Dispose();
                }
            }

            return files;

Answer 1

If you are saying your files collection has 4 items, but the 4 item contains no value, what do you mean by that? Is it null, does the object have no data, or does it throw an index out of range exception?

Are you doing a files[4] or something like the following?

for(int x = 1; x < files.length; x++)
{
     files[x]
}

That won't work. Remember 0 based indexing in C#.

As a side note, you could do away with your try catch statments by doing something like:

using (SqlConnection connection = new SqlConnection(conn_string))
{
    connection.Open();
    using (SqlCommand cmd = new SqlCommand("SELECT * FROM MyTable", connection))
    {
         using (SqlDataReader dr = cmd.ExecuteReader())
         {
             return result;
         }
    }
}

The using statement will guarantee disposal (and therefore the closing) of the reader and connection.

Answer 2

You should ditch "if (dr.HasRows)", all it does is duplicate the check in the while loop.

You shouldn't ever be calling Close on a connection, nor should you set it to null. Instead you should wrap the connection in a "using" block like so:

using (SqlCommand cmd = new SqlCommand()) {
   //use the connection
}

The same can be said for you data reader and SQL Command.

This next bit does nothing at all, delete it.

  catch (Exception) { throw; }