ASP.NET MVC UpdateModel意外失败

Question

I am trying to update some object properties by calling UpdateModel(myObject, new[] { "stringprop1", "stringprop2", "intprop"}) .

This is failing for an unknown reason. Several string properties are updating successfully. When I try to update an int property it fails. The new int value is being sent from an html select list on the view.

I can see the data from the view in my ValueProvider. The key matches the object's property name and the value is what I am expecting from the view (except that it's a string. I thought UpdateModel could handle simple type conversions.

When I call UpdateModel an InvalidOperationException is thrown, ONLY IF THE PROPERTY'S VALUE IS CHANGING.

Also, the object is a Linq To Sql generated object.

EDIT

Looking through Model State after calling TryUpdateModel, I see this exception on the property that I am having trouble with:

- Exception {"Operation is not valid due to the current state of the object."} System.Exception {System.Data.Linq.ForeignKeyReferenceAlreadyHasValueException}

The value I am trying to update is a foreign key. Why can't I update this value? Thanks for any help?

EDIT 2

I found this: http://social.msdn.microsoft.com/Forums/en-US/linqtosql/thread/f9c4a01a-195a-4f2b-a1cb-e2fa06e28b25

I could have sworn that I have changed the key instead of the association property before, but whatever. What can be done in this MVC Model Binding situation?

Answer 1

Screw it. I just did it the old fashioned way:

myObject.Skunk = db.Skunks.Single(s => s.ID == intprop);

Answer 2

I had this same problem and then realized it was the DataContext itself. I was saving this in session, rather than creating a new one with each request. Once I created the Context for each request, this error went away.

Answer 3

I came across this problem when I was using DataLoadOptions. Simply having DLO set for the column with foreign key was enough to cause this error. I fixed it by making a new instance of DataContext without DLO.

Note, that it made no difference that the value in the column with foreign key was set to null at the beginning of update.

I hope this helps someone who has a similar problem (this question was one of the first results that I came across when I was trying to solve it myself).