HTTP POST to Many to Many relation asp.net web api

[min0ru]

I am new to ASP.net (and programming in general) and am having trouble building a Web API. More specifically I need help in these two areas: [*]How to configure my "DOCcontroller" to post a new document (DOC table).[*]How to make the actual ajax post -- I am having trouble passing the EXT_GUID parameter.Essentially this is for a simple document management system. I want Get/Post documents (DOC) by having the user supply an GUID from an external database (the EXT_GUID field) as a filter/parameter. Each document can have multiple EXT_GUIDs and each EXT_GUID can have multiple Documents (DOC). You can assume that the EXT_GUID fields we be populated prior to the http post. Thank you very much in advanced, even if you just read about my problem!!!THIS IS THE DOCcontroller CODE\[code\] //POST api/DOC public HttpResponseMessage PostDOC(DOC doc, List<string> parentOwners) { if (ModelState.IsValid) { var parents = db.BIMs.Where(bx => parentOwners.Contains(bx.EXT_GUID)); foreach (var p in parents) doc.Owners.Add(p); db.DOCs.Add(doc); db.SaveChanges(); HttpResponseMessage response = Request.CreateResponse(HttpStatusCode.Created, doc); response.Headers.Location = new Uri(Url.Link("DefaultApi", new { id = doc.Id })); return response; } else { return Request.CreateResponse(HttpStatusCode.BadRequest); } }\[/code\]THIS IS MY MODEL SETUP -- EntityFramework codefirst stuff\[code\] public class EXT { public int Id { get; set; } public string EXT_GUID { get; set; } public int ProjectID { get; set; } public virtual ICollection<DOC> DOCs { get; set; } } public class DOC { public int Id { get; set; } public int ProjectID { get; set; } public string Subject { get; set; } public string Link { get; set; } public virtual ICollection<EXT> EXTs { get; set; } }\[/code\]//THIS is more Storage Model...\[code\] public StoreDBContext() : base("name=StoreDBContext") { } public DbSet<EXT> EXTs { get; set; } public DbSet<DOC> DOCs { get; set; } protected override void OnModelCreating(DbModelBuilder modelBuilder) { //Set FLUENT API config for many to many here modelBuilder.Entity<EXT>() .HasMany(a => a.DOCs) .WithMany() .Map(x => { x.MapLeftKey("EXT_Id"); x.MapRightKey("DOC_Id"); x.ToTable("EXTsDOCs"); }); }\[/code\]AJAX Code\[code\]function AddDOC() { var parentOwner = "{\"" + $('#txtaddEXT').val() + "\"}"; jQuery.support.cors = true; var DOC = { ProjectId: ProjectID, Subject: $('#txtaddDOCSubject').val(), Link: $('#txtaddDOCLink').val(), parentOwner: parentOwner }; $.ajax({ url: "http://localhost:54171/api/DOC/", type: 'POST', data: JSON.stringify(DOC), contentType: "application/json;charset=utf-8", success: function (data) { WriteResponse(data); }, error: function (x, y, z) { alert(x + '\n' + y + '\n' + z); } }); }\[/code\]