c# - ASP.NET MVC How to convert ModelState errors to json

Question

How do you get a list of all ModelState error messages? I found this code to get all the keys: ( Returning a list of keys with ModelState errors)

var errorKeys = (from item in ModelState
        where item.Value.Errors.Any() 
        select item.Key).ToList();

But how would I get the error messages as a IList or IQueryable?

I could go:

foreach (var key in errorKeys)
{
    string msg = ModelState[error].Errors[0].ErrorMessage;
    errorList.Add(msg);
}

But thats doing it manually - surely there is a way to do it using LINQ? The .ErrorMessage property is so far down the chain that I don't know how to write the LINQ...

Answer 1

You can put anything you want to inside the select clause:

var errorList = (from item in ModelState
        where item.Value.Errors.Any() 
        select item.Value.Errors[0].ErrorMessage).ToList();

EDIT: You can extract multiple errors into separate list items by adding a from clause, like this:

var errorList = (from item in ModelState.Values
        from error in item.Errors
        select error.ErrorMessage).ToList();

Or:

var errorList = ModelState.Values.SelectMany(m => m.Errors)
                                 .Select(e => e.ErrorMessage)
                                 .ToList();

2^nd EDIT: You're looking for a Dictionary<string, string[]>:

var errorList = ModelState.ToDictionary(
    kvp => kvp.Key,
    kvp => kvp.Value.Errors.Select(e => e.ErrorMessage).ToArray()
);