How to tell if SubmitChanges() will actually change anything for a particular entity in LINQ to SQL

Question

I'm trying to determine if any changes were made to a particular entity object. Essentially, I want to know if SubmitChanges() will actually change anything. I would prefer to be able to determine this after SubmitChanges() has been called, but it doesn't really matter.

Anyone know how I would do this?

Answer 1

Take a look at the GetChangeset function on your DataContext.

Answer 2

This is what I came up with:

Public Function HasChanges(ByVal obj As Object) As Boolean
    Dim cs = GetChangeSet()
    If cs.Updates.Contains(obj) Or cs.Inserts.Contains(obj) Or cs.Deletes.Contains(obj) Then Return True
    Return False
End Function

Answer 3

You can directly access the changes for an attached entity instance using the parent table:

var entityType = typeof(myEntity);
var table = dataContext.GetTable<entityType>();
var modifiedMembers = table.GetModifiedMembers(myEntity);

if (modifiedMembers.Any())
{
      ... changes were made
}
else
{
      ... no changes were made
}

BUT - you have to do it before SubmitChanges(), of course. I use this approach instead of GetChangeSet(), due to the better type fidelity, and the fact that you can easily inspect the changes themselves.