Question

Related to this: Adding new items dynamically to IQueryable hard-coded fake repository

How could I build the method for the following class, which would remove items from the list based on the value of one of its fields?

public class FakeProductsRepository 
{
  private readonly List<Product> fakeProducts = new List<Product>
  {
      new Product { ProductID = "xxx", Description = "xxx", Price = 1000 },
      new Product { ProductID = "yyy", Description = "xxx", Price = 2000 },
      new Product { ProductID = "zzz", Description = "xxx", Price = 3000 },
  };

  public void AddProduct(string productID, string description, int price)
  {
      fakeProducts.Add(new Product
      {
          ProductID = productID,
          Description = description,
          Price = price,
      });
  }

  public void RemoveProduct(string productID)
  {
      ????????
      //How to remove the item from the fakeProducts List where ProductID == productID?
  }

  public IQueryable<Product> Products
  {
      get { return fakeProducts.AsQueryable(); }
  }
}

The problem method is pointed out with “???????” and the comment string.

Answer 1

In general, for a collection I’d use this code:

var productsToRemove = fakeProducts.Where(p => p.ProductID == productID).ToList();
foreach(var product in productsToRemove)
{
   fakeProducts.Remove(product);
}

Don’t forget the ToList(), or you can get an InvalidOperationException saying “Collection was modified”.

Update (thanks to linuxuser27):
But List<T> also has a special method, taking Predicate<T>:

fakeProducts.RemoveAll(product => product.ProductID == productID);