CodeDom: ensure that referenced foreign key entities haven't been loaded.
CodeDom: ensure that referenced foreign key entities haven't been loaded.

Consider the following entity:

	partial class Employee {
		// foreign key value
		[Column(...)]
		public int EmployeeID {...}

		// entity property wrapper for the foreign key value
		[Association(...)]
		public Employee Employee {...}
	}

We don't support entities "changing" their foreign-key ID values IFF the
corresponding "entity property" has already been loaded.

For example, this is fine:

	var e = new Employee();
	e.EmployeeID = 1;
	e.EmployeeID = 2;

This is not:

	var e = new Employee();
	e.Employee = someOtherLoadedEmployeeEntity;
	e.EmployeeID = 2;

This follows existing CodeText behavior.


git-svn-id: 1800f71f313d917366f95485fa960eed04b40598@1385 33146b6e-df29-0410-a1ca-39be37fb9416

Sectoid/dblinq,sharique/dbinq,Sectoid/dblinq,sharique/dbinq