根据列表框选择从字典中删除项目

Question

I have a listbox that prints the name of a custom item class

public class Item
{
    public string @Url { get; set; }
    public string Name { get; set; }
    public double Price { get; set; }

    public Item(string @url, string name, double price)
    {
        this.Url = url;
        this.Name = name;
        this.Price = price;
    }

    public override string ToString()
    {
        return this.Name;
    }
}

I tried the normal method but because i have radio buttons to sort the list box it messes it up since index is changed.

EG

//new item is declared
Dictionary<int, Item> itemList = Dictionary<int, Item> { new Item("f.ca", "name1", 33);
                                                      new Item("m.ca", "name2", 44); }
//Items added to listbox
for (int v = 0; v < itemList.Count; v++)
{
    itemListBox.Items.Add(itemList[v].Name);
}

//start sorting
var priceSort = from item in itemList
                orderby item.Value.Price
                select new { item.Value.Name, item.Value.Price };

itemListBox.Items.Clear();
foreach (var i in priceSort)
{
    itemListBox.Items.Add(i.Name);
}              
//end sorting listbox updated

now that the new list is created removing only the item in itemlist is necessary since the box is updated.

/* This code is what i thought but SelectedIndex say if on 0 and since the sorted by price */
itemList.Remove(itemListBox.SelectedIndex);

The issue being now its trying to remove items[0] when items[1] is really the one that needs to be removed. Is there a way i could make it compare the string of the itemlistbox to the .Name property of the items dictionary?

Answer 1

You stated that the key for your dictionary is determined by the current count of items in the dictionary. If that's the case, you'd have to do something like this:

var matches = itemList.Where(x => x.Name == itemListBox.SelectedValue);
if (matches.Any())
{
    itemList.Remove(matches.First().Key);
}

But this is slow and inelegant. You're really not using the Dictionary class correctly. Dictionaries are ideal for performing quick access based on a known key value. If you have to search for the key every time, you loose all benefit the Dictionary provides.

You might as well use a simple List<Item> instead, using the FindIndex / RemoveAt methods:

var index = itemList.FindIndex(x => x.Name == itemListBox.SelectedValue);
if (index != -1)
{
    itemList.RemoveAt(index);
}

This isn't a whole lot faster, but it's more elegant—lists are specifically designed to support this kind of thing without having to resort to Linq.

Or better yet, use the item's name as the dictionary key:

Dictionary<string, Item> itemList = Dictionary<string, Item>();
itemList.Add("name1", new Item("f.ca", "name1", 33));
itemList.Add("name2", new Item("m.ca", "name2", 44));

...

itemList.Remove(itemListBox.SelectedValue);

This is a much more efficient and elegant solution.