Pass list of categories to partial view - asp.net-mvc

Question

I have a partial view which will display list of Main Categories and under each Main Category all of its subcategories. But the problem is I don't know how can I pass this Category List to my partial view. Please check the code bellow. I've also attached my .edmx table map picture to give you better idea. Once I pass it to partial view I want to loop though all categories and sub categories to display them
[ChildActionOnly]
public PartialViewResult _GuestNav()
{
using (var db = new TestEntities())
{
db.Categories.ToList(); // get list from here
return PartialView("_GuestNav"); // then pass that list to partial view
}
}

Answer 1

Here is the main action code:
public ActionResult Categories()
{
using (var dbCtx = new DbContext())
{
var categories = dbCtx.Categories.Include(x => x.SubCategories).ToList()
return View(categories);
}
}
Then in your Categories.cshtml you will have the code as below:
#model IEnumerable<Categories>
<ul>
#foreach(var category in Model)
{
<li>#category.CategoryName
#if(category.SubCategories.Any())
{
Html.RenderPartial("~/Partial/_SubCategory.cshtml", category.SubCategories);
}
</li>
}
</ul>
At last you supply a partial view called _SubCategory.cshtml in the Partial folder of Category folder as below:
#model IEnumerable<SubCategory>
<ul>
#foreach(var subCategory in Model)
{
<li>#subCategory.SubCategoryName</li>
}
</ul>
In your case if you want to pass this list to the partial view you specified you can do it as below:
[ChildActionOnly]
public PartialViewResult _GuestNav()
{
using (var db = new TestEntities())
{
var categories = db.Categories.Include(x => x.SubCategories).ToList(); // Added the include if you want to add subcategories as well
return PartialView("_GuestNav", categories); // then pass that list to partial view
}
}

Answer 2

Yo can use model binding, pass a Model or ViewModel as a parameter and access it from the partial view. For example, in your _GuestNav action:
...
return PartialView("_GuestNav",db.Categories.ToList());
Here's a link on how to accomplish that.
Then you can bind the model in your view. For example:
...
#model IEnumerable<Categories>;
For more detail, check out the examples from the link.

Answer 3

The PartialView method has an override that accepts an object. You need to store the results of the db.Categories.ToList() call in a variable and pass that to the method like this:
using (var db = new TestEntities())
{
var cats = db.Categories.Include("SubCategories").ToList(); // get list from here
return PartialView("_GuestNav", cats); // then pass that list to partial view
}
Just make sure your partial view expects a list of categories as its model. Then, inside your view you can iterate over the model and display the subcategories.
You should also look into how to use a viewmodel for your views.
EDIT
You may need to use an include statement since navigation properties are generally lazy loaded. Updated my answer.