OK, I figured out one solution.
On my Grid, I added a GridEvents section;
<GridEvents OnActionBegin="BeginHandler" TValue="TierPrice"></GridEvents>
Then in my code, I added the following;
protected void BeginHandler(ActionEventArgs<TierPrice> args)
{
if (args.RequestType == Syncfusion.Blazor.Grids.Action.Save)
{
if (args.Data.Id == Guid.Empty)
{
args.Data.Id = Guid.NewGuid();
}
}
}
This seems to work the way I want.