Custom Validation Message from Controller to View

Question

I have a link in page, that when clicked by a user sends a post to the Controller. The controller accepts a single int value. This is the id of the item in the View.

The Model in the View is an IEnumerable Type.

I need my controller to do a check on the item and validate it against another model. This is a custom model and has no Views. I have tried:

@Html.ValidationSummary(true, "Validation Summary Error!")

It does not work because I am using an IEnumerable Type.

My Question is, how do I send a message back to the View from the Controller if a situation is met in the Controller?

[ EDIT ] I am using a WebGrid to display the items. This is why I am using an IEnumerable Type Model in my View.

Answer 1

The ValidationSummary will display all ModelState errors, so you can add random ones with an empty key for situations like this:

if (!condition) {
    ModelState.AddModelError("", "Validation error!");
}