You can use IsLoading property of our new component RadzenDataGrid. Iβve just noticed that the property is not exposed in Radzen property grid however it will be in our next update early next week - in the meantime you can set it using Attributes. Please take a note that IsLoading will require binding using LoadData event and will not work automatically with IQueryable binding.
the reason I asked is because my VS and Rider IDE's both flag it as not being there, even though I just updated to the latest Radzen.Blazor version this morning.
It is also worth mentioning that the RadzenDataGrid itself does not set the IsLoading property. When it is set by the developer the RadzenDataGrid displays a built-in loading indicator. This is visible on this demo: https://blazor.radzen.com/datagrid-odata
You seem to need something else considering the latest code that you have provided - some indication of when the DataGrid fetches data. This isn't provided as a built-in feature. You could probably simulate it by using the LoadData event.
It's quite simple what I'm trying to achieve, basically a loading indicator that appears before and during the data load, then disappears and reveals the grid once the load has finished.
I apologise I didn't notice the Subtle renaming "RadzenGrid" vs "RadzenDataGrid" I'll take a look at the new one.
For the time being though (After todays sprint anyway) I've now come up with a work around. It's a lot more mark-up and code, but it handles the case quite succinctly.