lambda expression Problems - asp.net-mvc

Question

My question is when I click actionlink,the view send specific ID to controller(ex. ProductID = 6), but my controller grab all data to me not specific ID data.
I think the problem is the lambda expression at controller, it will grab all data to me.
These are my Models:
public class ShoppingCart
{
public List<ShoppingCartItemModel> items = new List<ShoppingCartItemModel>();
public IEnumerable<ShoppingCartItemModel> Items
{
get { return items; }
}
}
public class ShoppingCartItemModel
{
public Product Product
{
get;
set;
}
public int Quantity { get; set; }
}
Controller :
[HttpGet]
public ActionResult EditFromCart(int ProductID)
{
ShoppingCart cart = GetCart();
cart.items.Where(r => r.Product.ProductID == ProductID)
.Select(r => new ShoppingCartItemModel
{
Product = r.Product,
Quantity = r.Quantity
});
return View(cart);
//return RedirectToAction("Index", "ShoppingCart");
}
private ShoppingCart GetCart()
{
ShoppingCart cart = (ShoppingCart)Session["Cart"];
//如果現有購物車中已經沒有任何內容
if (cart == null)
{
//產生新購物車物件
cart = new ShoppingCart();
//用session保存此購物車物件
Session["Cart"] = cart;
}
//如果現有購物車中已經有內容,就傳回 view 顯示
return cart;
}
View
#model ShoppingCart
#{
ViewBag.Title = "購物車內容";
}
<h2>Index</h2>
<table class="table">
<thead>
<tr>
<th>
Quantity
</th>
<th>
Item
</th>
<th class="text-right">
Price
</th>
<th class="text-right">
Subtotal
</th>
</tr>
</thead>
<tbody>
#foreach (var item in Model.items)
{
<tr>
<td class="text-center">
#item.Quantity
</td>
<td class="text-center">
#item.Product.ProductName
</td>
<td class="text-center">
#item.Product.Price.ToString("c")
</td>
<td class="text-center">
#( (item.Quantity * item.Product.Price).ToString("c"))
</td>
<td>
#using (Html.BeginForm("RemoveFromCart", "ShoppingCart"))
{
#Html.Hidden("ProductId", item.Product.ProductID)
#*#Html.HiddenFor(x => x.ReturnUrl)*#
<input class="btn btn-warning" type="submit" value="Remove">
}
</td>
<td>
#using (Html.BeginForm("EditFromCart", "ShoppingCart", FormMethod.Get))
{
#Html.Hidden("ProductId", item.Product.ProductID)
<input class="btn btn-warning" type="submit" value="Edit">
}
</td>
</tr>
}
</tbody>
</table>

Answer 1

The key issue is that this code doesn't return the result of the LINQ queries, because you have not assigned a variable to the result:
cart.items.Where(r => r.Product.ProductID == ProductID)
.Select(r => new ShoppingCartItemModel
{
Product = r.Product,
Quantity = r.Quantity
});
I strongly suggest you create a viewmodel specifically to display the cart items.
public class CartItemsViewModel
{
public List<ShoppingCartItemModel> Items { get; set; }
}
[HttpGet]
public ActionResult EditFromCart(int ProductID)
{
ShoppingCart cart = GetCart();
var viewModel = new CartItemsViewModel();
viewModel.Items.AddRange(cart.items.Where(r => r.Product.ProductID == ProductID)
.Select(r => new ShoppingCartItemModel
{
Product = r.Product,
Quantity = r.Quantity
}));
return View(viewModel);
}
In my example I use the .AddRange() method to take the results of the LINQ calls against the cart items and store them in the viewmodel's Items property.

Answer 2

You must have to assign filtered value to cart like this.
cart.item = cart.items.Where(r => r.Product.ProductID == ProductID)
.Select(r => new ShoppingCartItemModel
{
Product = r.Product,
Quantity = r.Quantity
}).ToList();
use ToList(); or FirstOrDefault() as per your condition

Answer 3

You need to hold the return value from the linq query on cart.Items in a variable and pass that to the View method.
At the moment, the result of your query is being lost and the whole cart passed to the View method.