Question

Here is the view code:

@helper sortLink(string name, int id)
{
<a href="@Url.Action("Products", "Home", new { sortBy = id, isasc = (id ==     ViewBag.sortBy ? !@ViewBag.isAsc : @ViewBag.isAsc).ToString().ToLower() })">@name</a> 
}

<h2 class="center">Products</h2>

<table class="Products">
@* header *@

<tr>
<th>@sortLink("ID",1)</th>
<th>@sortLink("Name",2)</th>
<th>@sortLink("Number", 3)</th>
<th>@sortLink("Color", 4)</th>
<th>@sortLink("Standard Cost", 5)</th>
<th>@sortLink("List Price", 6)</th>
<th>@sortLink("Size", 7)</th>
<th>@sortLink("Weight", 8)</th>
</tr>

This is the controller code :

  {
    AdventureWorksLT2008R2Entities db = new AdventureWorksLT2008R2Entities();
    const int pageSize = 10;

    [HttpGet]
    public ActionResult Products(int page = 1, int sortBy = 1, bool isAsc = true)
    {
        IEnumerable<Product> products;

        #region sorting
        switch (sortBy)
        {
            case 1:
                products = isAsc ? db.Products.OrderBy(p => p.ProductID) : db.Products.OrderByDescending(p => p.ProductID);
                break;

            case 2:
                products = isAsc ? db.Products.OrderBy(p => p.Name) : db.Products.OrderByDescending(p => p.Name);
                break;

            case 3:
                products = isAsc ? db.Products.OrderBy(p => p.ProductNumber) : db.Products.OrderByDescending(p => p.ProductNumber);
                break;

            case 4:
                products = isAsc ? db.Products.OrderBy(p => p.Color) : db.Products.OrderByDescending(p => p.Color);
                break;

            case 5:
                products = isAsc ? db.Products.OrderBy(p => p.StandardCost) : db.Products.OrderByDescending(p => p.StandardCost);
                break;

            case 6:
                products = isAsc ? db.Products.OrderBy(p => p.ListPrice) : db.Products.OrderByDescending(p => p.ListPrice);
                break;

            case 7:
                products = isAsc ? db.Products.OrderBy(p => p.Size) : db.Products.OrderByDescending(p => p.Size);
                break;

            case 8:
                products = isAsc ? db.Products.OrderBy(p => p.Weight) : db.Products.OrderByDescending(p => p.Weight);
                break;
        }
        #endregion

        products = db.Products
            .OrderBy(p=>p.ProductID)
            .Skip((page - 1) * pageSize)
            .Take(pageSize)
            .ToList();

        ViewBag.CurrentPage = page;
        ViewBag.PageSize = pageSize;
        ViewBag.TotalPages = Math.Ceiling((double)db.Products.Count()/pageSize);

        return View(products);

I am following a tutorial and struck on the sorting part where it keeps showing this error,
i need your help to get remove the error and please explain whats going on the Sortlink helper method, i wan’t able to understand it well. The person who wrote this tutorial didn’t explain much on this part.

Answer 1

I’m guessing the problem is that you’re trying to use ViewBag.isAsc in the view, but never assigned it. Also, after the case statement, you’re resetting the products variable, which completely invalidates the ordering you set up in the case statement– remove that. So after it should look like this:

switch(sortBy) {
    // include all the case statements here as you have them

    // you need to add a default section to make it a valid switch statement
    default:
    break;
}
#endregion

// (remove the products = statement that was here, it's not needed

ViewBag.CurrentPage = page;
ViewBag.PageSize = pageSize;
ViewBag.TotalPages = Math.Ceiling((double)db.Products.Count()/pageSize);

// add these two lines, as required by the View
ViewBag.isAsc = isAsc;
ViewBag.sortBy = sortBy;


return View(products
    .Skip((page - 1) * pageSize)
    .Take(pageSize)
    .ToList()
);