如何捕获组合框SelectedValue绑定引发的FormatException

Question

I have a combobox with a simple binding:

SelectedValue="{Binding Path=SomeValue, Mode=TwoWay}

The problem is that SomeValue is sometimes a string not parsable to int. And I get " System.FormatException: Input string was not in a correct format. " as soon as I set the ItemsSource.

First question: how to handle the exception since I get a error message box. Second question: can I show kind of a validation error to the user?

Attention: the source of the problem comes from the view model data source so I don't think it has anything to classical validation patterns.

Answer 1

Create a dummy converter and put it into the debugger and put a breakpoint into it. It will become obvious what is wrong, types will be different. Use Snoop to determine the error logs by holding control shift and selecting that element and look under SelectedValue property.