Sequence contains more than one element in ASP.NET MVC

Question

I want to display products using single subcategory name but I am getting Sequence contains more than one element error.

SubCategory Name passes value to show action of Product controller which is like this

 public ActionResult show(string subcategory)
        {
            if (subcategory == null)
            {
                return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
            }


            var subcat = db.SubCategories.Include("Products").Single(s => s.SubCategoryName == subcategory);

            if (subcat == null)
            {
                return HttpNotFound();
            }

            return View(subcat);
        }

I have a menu view like this,

@model IEnumerable<mTest.Models.Category>

<div>
    <ul>
            @foreach (var category in Model)
            {
                <li class="active has-sub"><a href="#"><span>@category.CategoryName</span></a>
                    <ul>
                        @foreach (var subcategory in category.SubCategories)
                        {
                            <li class="has-sub"><a href="/Products/show?subcategory=@subcategory.SubCategoryName"><span>@subcategory.SubCategoryName</span></a></li>

                        }
                    </ul>

                </li>
            }
      </ul>
</div>

and Category, subcategory & product model like this

public class Category
    {
        public Category()
        {
           Products = new HashSet<Product>();
           SubCategories = new HashSet<SubCategory>();
        }
        public int CategoryId { get; set; }

        public string CategoryName { get; set; }



        public virtual ICollection<SubCategory> SubCategories { get; set; }

        public virtual ICollection<Product> Products { get; set; }
    }

public class SubCategory
    {
        public SubCategory()
        {
            Products = new HashSet<Product>();
        }

        public int SubCategoryId { get; set; }
        public string SubCategoryName { get; set; }

        public int CategoryId { get; set; }

        public virtual Category Category { get; set; }
        public virtual ICollection<Product> Products { get; set; }

    }

public class Product
    {

        public int ProductId { get; set; }
        public string ProductName { get; set; }



        public int CategoryId { get; set; }

        public int SubCategoryId { get; set; }

        public virtual Category Category { get; set; }

        public virtual SubCategory SubCategory { get; set; }

    }

I have Data on subcategory is like this

|Computer=>HP
         =>Lenovo
|Computer=>HP
         =>Lenovo

|Mobile  =>Samsung
         =>Apple
|Mobile  =>Samsung
         =>Apple

How to solve this issue.

Answer 1

var subcat = db.SubCategories.Include("Products").Single(s => s.SubCategoryName == subcategory);

If more than one element is found in SubCategories for a given subcategory , then because of Single usage, above statement will throw error mentioned by you (Sequence contains more than one element). So instead of using Single , use FirstOrDefault . So your code should be as shown below.

var subcat = db.SubCategories.Include("Products").FirstOrDefault(s => s.SubCategoryName == subcategory);