GridView: Creating groups and summaries with 2 lines of code

GridView has a lot of improvements over the DataGrid but it still lacks some very important features. A recurring requirement not available in the GridView is to create groups and summaries. To create summaries we can easily code the RowDataBound event. Grouping is a more complex task, and involves more coding and debugging. But when we need to combine these two features the things really start to get messy. With this in mind I have implemented the GridViewHelper, as the name suggests, a helper class to aid the creation of groups and summaries.