GridView performance and memory issues

Hello, Ignacio, 

Straight to your questions:

1. When you set the IsExpanded property to true for a row, note that it makes a refresh operation in the grid. Hence, the more rows are expanded, the more refresh operations will be performed. The possible solution that I can suggest for this case is to use BeginUpdate/EndUpdate block while the rows are set as expanded. Thus, only one refresh operation will be performed at the end: 

            this.radGridView1.BeginUpdate();
            foreach (GridViewRowInfo r in this.radGridView1.Rows)
            {
                r.IsExpanded = true;
            }
            this.radGridView1.EndUpdate();

Additional tips for improving the performance are setting the UseScrollbarsInHierarchy property to true, the TableElement.RowScroller.ScrollMode property to ItemScrollerScrollModes.Deferred. Deferred scrolling updates the view only when the scrollbar thumb is released. A tooltip helps indicating the position to which the view will be scrolled to.

2. We haven't had similar memory concerns about RadGridView form other customers. 

I would like to let you know that our controls provide rich UI capabilities and theming mechanism which inevitably increases the memory usage. Furthermore, our components are built from the Telerik Presentation Framework which is built on top of the .NET Framework which once again, inevitably increases memory usage compared to other controls, such as the standard controls which simply wrap native objects.  Unless a certain control has a memory leak, it is eventually being disposed. Calling GC.Collect will not dispose the objects immediately, they will simply be marked for disposal and the next time the Garbage Collector passes by it will decide whether they are suitable for actual disposal. This is due to the non-deterministic behavior of the Garbage Collector. Our objects are mostly from Generation 3, which means that they will be disposed at a later state (more about garbage collection).

The memory leak might be caused by the fact that you are showing a new Form instance every time with the ShowDialog method. A quote from MSDN says: "Unlike modeless forms, the Close method is not called by the .NET Framework when the user clicks the close form button of a dialog box or sets the value of the DialogResult property. Instead the form is hidden and can be shown again without creating a new instance of the dialog box. Because a form displayed as a dialog box is not closed, you must call the Dispose method of the form when the form is no longer needed by your application." 

If you are still experiencing any further problems related to memory consumption, I would kindly ask you to submit a support ticket from your Telerik account where you can provide a sample project demonstrating the problem. Thus, we would be able to make an adequate analysis of the precise case and provide further assistance. Thank you in advance.

I hope this information helps. If you need any further assistance please don't hesitate to contact me. 

Regards,
Dess | Tech Support Engineer, Sr.
Progress Telerik