Question

I’m querying the Asp.NET MVC ModelStateDictionary using LINQ but I’m stuck on the following query:

public static DirectResult DirectValidation( this ModelStateDictionary state )
    {
        return new DirectResult()
        {
            Data = new
            {
                success = false,
                errors = from e in state
                        where e.Value.Errors.Count > 0
                        let errorName = e.Key
                        select new
                        {
                            errorName = e.Value.Errors.Select( x => x.ErrorMessage ).Concat( e.Value.Errors.Where( x => x.Exception != null ).Select( x => x.Exception.Message ) )
                        }

            }
        };

    }

In particular, I want the variable errorName to appear on the left hand side of the assignment. However, currently as things stand, what is getting output is:

"errors": [
  {
    "errorName": [
      "Code must be unique"
    ]
  }
]

How must I write the LINQ in order to get the result that I would like i.e something like

"errors": [
  {
    "Code": [
      "Code must be unique"
    ]
  }
]

Answer 1

The problem is that the thing on the left hand side is a member name, and in statically-typed languages, member names are fixed. You could try to create a type dynamically or, if you have access to C# 4, use an ExpandoObject.

object CreateExpando(string field, object o)
{
    var e = new ExpandoObject();
    var d = e as IDictionary<string, object>;
    d[field] = o;
    return e;
}

select CreateExpando(errorName, e.Value.Errors.Select...);