Create Master detail with Entity framework - asp.net-mvc-3

Question

I have a blogPost that should take the category name and to do this I've done like this in get action :
public ActionResult Add()
{
ViewBag.CategoryList = new SelectList(_categoryRepository.GetAllCategory(), "Id", "Name");
return View(new BlogPost());
}
and in the View I have :
#model Blog.Domain.Model.BlogPost
#{
ViewBag.Title = "AddPost";
Layout = "~/Areas/Admin/Views/Shared/_AdminLayout.cshtml";
}
<fieldset>
#using (Html.BeginForm("Add", "Blog", FormMethod.Post))
{
#Html.ValidationSummary()
<div>
#Html.LabelFor(b => b.Title)
#Html.TextBoxFor(b => b.Title)
#Html.ValidationMessageFor(b => b.Title)
</div>
<div>
#Html.LabelFor(b => b.Body)
#Html.EditorFor(b => b.Body)
#Html.ValidationMessageFor(b => b.Body)
</div>
<div>
#Html.LabelFor(b => b.Summary)
#Html.TextBoxFor(b => b.Summary)
#Html.ValidationMessageFor(b => b.Summary)
</div>
<div>
#Html.LabelFor(b => b.Category)
#Html.DropDownListFor(model => model.Category.Id, ViewBag.CategoryList as SelectList, "--- Select Category ---", new { #class = "some_class" })
</div>
<div>
<input type="submit" value="Add Post" />
</div>
}
</fieldset>
and in the Post action I have write this code :
[HttpPost]
public ActionResult Add(BlogPost blogPost)
{
if (ModelState.IsValid)
{
blogPost.PublishDate = DateTime.Now;
_blogPostRepository.AddPost(blogPost);
_blogPostRepository.Save();
return View();
}
return View();
}
I'm not sure that I have written this code exactly correct or not , but I have this trouble for a lone time ! master detail inserting with entity framework actually in this case selecting a category and sending it to database successfully , if you have write something like this before please help me about that, thanks

Answer 1

Looks like you're setting up two drop down lists and assigning the value of one to the model's ID field, which I assume is the ID of the blog post entity..?
Remove the #Html.DropDownList(...) statement
Modify the first parameter of #Html.DropDownListFor(...) to a lambda expression selecting the CategoryId property of the model/entity (whatever the FK field name is for Category, presumably model => model.CategoryId)
#Html.LabelFor(b => b.Category)
#Html.DropDownListFor(model => model.CategoryId, ViewBag.CategoryList as SelectList, "--- Select Category ---", new { #class = "some_class" })