ModelState AddModelError - How can I add an error that isn t for a property

Question

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

User · Answer

You can add the model error on any property of your model, I suggest if there is nothing related to create a new property.

As an exemple we check if the email is already in use in DB and add the error to the Email property in the action so when I return the view, they know that there's an error and how to show it up by using

<%: Html.ValidationSummary(true)%>
<%: Html.ValidationMessageFor(model => model.Email) %>

and

ModelState.AddModelError("Email", Resources.EmailInUse);

User · Answer

Putting the model dot property in strings worked for me  ModelState AddModelError  Item1 Month    This is not a valid date

User · Answer

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  lt    Html ValidationSummary     gt  as you d expect

[asp.net-mvc-2] ModelState.AddModelError - How can I add an error that isn't for a property?

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