Getting the string-value from foreign key - sql

Question

I got two classes in my blog-app:
public class Post
{
public int PostId { get; set; }
public int CategoryId { get; set; }
public string PostImg { get; set; }
public virtual ICollection<Comment> Comments { get; set; }
//some other stuff
}
public class Category
{
public int CategoryId { get; set; }
public string CategoryName { get; set; }
public string Slug { get; set; }
public string Description { get; set; }
}
As you can see, the post has an int property representing its category. I would like my index-method to be able to take a parameter that can sort the posts by category depending on what is clicked in the view. If category had been a string property directly in my postclass, this would not have been a problem. But now that its only an int, i fail to see how to accomplish this.
Lets say I have a mthod that looks something like this:
public ActionResult Index(string category)
{
var model = new IndexViewModel
{
Posts = _repository.Posts.Where(o=>o.CategoryId == category).ToList(),
};
return View(model);
}
Of course the above does not work cos categoryId is an int and category is a string. I hope someone can see what im trying to do here.
Thanks!

Answer 1

You need to use join statement to get the post which has category with the given name. I assume that category in the parameter is the category name. Otherwise the answer given by Giannis is correct.
public ActionResult Index(string category)
{
var model = new IndexViewModel
{
Posts =_repository.Posts.Join(_repository.Categories.Where(c => c.CategoryName == category), p => p.CategoryId, c => c.CategoryId, (p, c) => p).ToList(),
};
return View(model);
}

Answer 2

You may either declare your argument as int:
public ActionResult Index(int category)
{
var model = new IndexViewModel
{
Posts = _repository.Posts.Where(o=>o.CategoryId == category).ToList(),
};
return View(model);
}
Or parse it into a variable:
public ActionResult Index(string category)
{
var categoryId = Int32.Parse(category);
var model = new IndexViewModel
{
Posts = _repository.Posts.Where(o=>o.CategoryId == categoryId).ToList(),
};
return View(model);
}