When VirtualLoad™ and GroupedColumns features are enabled (assuming that VirtualPageSize property is set to 50), WebGrid will try to keep the number of loaded rows not more than 50 rows (to match with the VirtualPageSize property).

WebGrid will try to expand grouped columns one by one starts from first row and then count the number of loaded rows. After expanding the grouped columns, WebGrid will count how many loaded rows. If the amount of loaded rows is less than 50, then WebGrid will keep this grouped colum expanded; and then try to expand the next grouped column and do counting again. If the amount of loaded rows is exceeding than 50 rows, then WebGrid will collapse the last grouped column.

When group columns exist in top level Table, all parent group rows will be rendered to clients but only a number of defined rows are rendered counted from the first parent group row. When users click on “+” to expand group row, the control will transparently and virtually load the child rows of that group row.

I have forwarded the “Expand” and “Expand All” minor glitch to WebGrid development team. A work item, work item #718, has been submitted regarding this issue. I’ll keep you updated with any news I heard from the team regarding this.

This behavior is not a bug and is by design.

When a virtual group is loaded, the “Expand All” command can expand the groups automatically. However, the groups that haven’t been fetched won’t be expanded. This is to avoid performance problem if there are a lot of groups that need to be fetched from server.

Please let us hear your response.

Can this be controlled on a WebGrid property like "IgnoreVirtualLoadModeOnGroupExpandAll"?  Even if the default is to only load 50.  There are some scenarios where I need the user to be able to finish loading all records underneath all groups and automatically expand them.

I need to discuss this feature request with WebGrid development team.
I’ll get back to you after I heard something from the team.

Thank you for your valuable feedback.