I believe I have seen this someplace before. I believe this is a way, based on knowing the text you are going to put in a control (say a label), that you can ask Xamarin Forms to tell you what the size of the control would be. If I recall correctly you used somaline like OnDevice and had to pass in the Text and the type of control. I just can't seem to find this now. Does anyone know if this is possible?
To be clear I am trying to address a defect in a third party control (SyncFusion DataGrid) I am using where the control is not sizing a grid column correctly. I was trying no to wait until the fix we released but I guess I will have to.
Syncfusion actually posted an updated that does finally seem to fix the problem of the columns not being sized correctly by width. I can't close this so I will just mark this as the answer.
For Syncfusion you can now do this:
mydatagrid.GridColumnSizer.Refresh();
mydatagrid.WidthRequest = mydatagrid.GetVisualContainer().ExtentWidth;