I had the same issue in general on Blazor with a text box, they are fixing this in 3.1 https://github.com/aspnet/AspNetCore/issues/11914
. There is a workaround and I have confirmed that textboxs on 3.1 textboxes work without the workaround. I'm doing a trial of Telerik's Blazor components and noticed the same validation issue existed so I had to put back in the workaround to fix it. It would be nice if this workaround wasn't required.