In the current build of WebGrid 7, the aggregate value will apply the format that specified in ‘DataFormatString’ property. So the aggregate value will have the same format as the data column.

A workaround that you may try is by manually accessing the element of the column footer and obtain the number shown in the column footer. Next, you can utilize the toFixed(n) method of javascript to format the number to use a specified number of trailing decimals defined by the n variable.

Hope this helps.

Hmmm, that's a real shame (

Do you think I can do something through defining a CustomAggreagate?  Would I be able to format the value that way?

I’ve forwarded this question to WebGrid development team to be investigated further.
I’ll keep you updated with any news I heard from the team regarding this matter.

I have submitted this specific scenario as feature request to WebGrid development team.

A task, task #746, has been submitted to the team regarding this feature. The team will check the feasibility to implement this feature in the next upcoming build of WebGrid 7.

Defining CustomAggregate will not helps as long as the aggregate result is placed in the column footer of WebGrid. the other option is to show the aggregate result in group header where you can define the format string of your aggregate result.