实体框架与 .NET 4.0 多对多关联

Question

I am new to .NET and EF and I'm working on an application that requires dynamic querying of the entities. I have a db with 3 tables:

**Employee**      **EmployeeSkills**      **Skill**
Employee_ID       Id                      Skill_ID
Name              Employee_ID             Name
Address           Skill_ID                etc.
etc.              Level

I will be sending from my client property names for selecting and dictionaries with property-value pairs for filtering, for example {"name", "skill",[{"skillId="1"},{"level=2"}]} will return all employees having the skill assoctiated with id 1 and konoledge of this skill at level 2.

I really need to design my entities so that the queries are as simple as possible, meaning no joins or complex sql's. I already managed to implement everything for selecting and filtering properties but I'm still struggling with many-to-many relationships.

I know that if my intermediary table would have only the Employee_ID and Skill_ID fields then i could just reference the skills using Employee.Skills.Is there any way to to this using my current table structure?

I'm hoping there is some kind of mapping, like defining some kind of navigation properties on the Employee entity that stores the query required to get all the Skills of an Employee with their Level.

PS I'm using VS 2012, EF runtime version 4.0.3, version 4.4.0

Answer 1

If you use codefirst approach, you can configure your relationship with Fluent API:

HasMany(e => e.Skills).WithMany(s=>s.Employees).Map(se =>
            {
                se.MapLeftKey("Skill_ID");
                se.MapRightKey("Employee_ID");
                se.ToTable("EmployeeSkills");
            });

Update In DB-First approach, you cannot configure navigation properties in your case. This is link where yu can read what you can do in your situation.