How to change default validation error message in ASP.NET MVC?

Solution 1:

Apparently my question was already answered at How to replace the default ModelState error message in Asp.net MVC 2? .

I'll summarize it here:

• Create App_GlobalResources folder for your project (right click to project -> Add -> Add ASP.NET folder -> App_GlobalResources).
• Add a resx file in that folder. Say MyNewResource.resx.
• Add resource key PropertyValueInvalid with the desired message format (e.g. "content {0} is invalid for field {1}"). If you want to change PropertyValueRequired too add it as well.
• Add the code DefaultModelBinder.ResourceClassKey = "MyNewResource" to your Global.asax startup code.

You're all set.