Caliburn Micro: Disable button on form validation error

I have a form with a textbox bound to an integer, and a button. Now, when the value of the textbox is invalid, I want to immediately disable the button.

Normally, one would put a Can() method in the VM, and trigger a NotifyOfPropertyChange in the 开发者_如何学运维property's setter. However, if the user inputs a non numeric value for example, the textbox is invalid, but the property setter is never called, so I can't notify/disable the button.

So, how do I disable the button, when the user inputs an invalid value that doesn't cause the property setter to get called? My knowledge of CM is limited as I've just started out.

I've found the best approach to this problem is to make the property a string instead and do the necessary string to integer conversion in your property setter. If the conversion is invalid, then you could reset the TextBox value to a default value. This way your property setter will always get fired.

If your model has an integer property, then it makes sense to place the string version on the view model, as this is only really related to the UI, rather than business logic.

If you don't wish the user to be able to input non digit characters, then you can use a masked text box, such as the one included in the Extended WPF Toolkit, or in a third party control suite such as those offered by Telerik or Infragistics.

I'd use a MaskedTextBox instead and set the mask to integer only.