asp.net-mvc-2asp.net-mvc-2-validationmodelstate

ModelState.AddModelError - How can I add an error that isn't for a property?


I am checking my database in Create(FooViewModel fvm){...} to see if the fvm.prop1 and fvm.prop2 already exist in that combination; if so, I want to add an error to the modelstate, then return the whole view. I tried:

public ActionResult Create(FooViewModel fvm){
    if (ThatComboAlreadyExists(fvm)) {
      ModelState.AddModelError("Model", "There is already one like that");
      return View(fvm);
    }
}

...but I get no display of errors in the Html.ValidationSummary, which is where I assume they would appear. I have the suspicion that "Model" is not the right key, but I haven't been able to find anything a la Google.


Solution

  • I eventually stumbled upon an example of the usage I was looking for - to assign an error to the Model in general, rather than one of it's properties, as usual you call:

    ModelState.AddModelError(string key, string errorMessage);
    

    but use an empty string for the key:

    ModelState.AddModelError(string.Empty, "There is something wrong with Foo.");
    

    The error message will present itself in the <%: Html.ValidationSummary() %> as you'd expect.