Slow performance with new Select (ParamArray of Collumns) and Execute as Collection

I use the SubSonic Select Command to query a table with about 20 rows and bind the result to a combobox. The statement looks something like this (sorry, VB Code):

ComboBox1.DataSource = New [Select]() _
                    .From(TableObject.Schema).OrderAsc(TableObject.NameColumn.PropertyName) _
                    .ExecuteAsCollection(Of TableObjectCollection)()

Execution Time: about 2 ms

Today I thought I could improve the execution time, if I only query the columns I need (Id, Name) and changed the statement to

ComboBox1.DataSource = New [Select](TableObject.IdColumn, TableObject.NameColumn) _
                    .From(TableObject.Schema).OrderAsc(TableObject.NameColumn.PropertyName) _
                    .ExecuteAsCollection(Of TableObjectCollection)()

Execution Time 300 ms

As you can see, the amount of time increases, I expected the opposite.
If I change the code to ExecuteDataSet the Performance is good again:
ComboBox1.DataSource = New [Select](TableObject.IdColumn, TableObject.NameColumn) _
                    .From(TableObject.Schema).OrderAsc(TableObject.NameColumn.PropertyName) _
                    .ExecuteDataSet()

Execution Time: 2 ms

So I thought the problem could be related to the generation of the sql code, but for every statement the code:
dim s as [Select] = new [Select]....
dim sql as string = s.BuildSqlStatement

renders in no time.
I am a little confused about this.

Oh, just to mention: MySql MYISAM Table, SubSonic DAL generated in C#, Gui in VB, SubSonic 2.1.1 from trunk

Update:

I found out that the execution only takes 300ms in debug mode, this is because a "System.IndexOutOfRangeException" occures during execution of dataReader[col.ColumnName] for every column that is not used in the query:
            foreach(TableSchema.TableColumn col in BaseSchema.Columns)
            {
                try
                {
                    SetColumnValue(col.ColumnName, dataReader[col.ColumnName]);
....

RecordBase.cs, ~ line 820): function Load(IDataReader dataReader)

Don´t know how to realize this (the dataReader has not .Contains Method), but SetColumnValue should only be executed for columns that are in the reader.