CODEWITHSUNDEEP
c#dictionary
Liam de Haas
Liam de Haas

Reputation: 1268

Add to value in Dictionary

I have a Dictionary<Product, int> Inventory which holds the inventory for the products that are in the shop.

How do I get the value that corresponds with the Product and add 1 to it?

It is also possible that the Product isn't in the dictionary.

Upvotes: 1

Views: 124

Answers (2)

user743382
user743382

Reputation:

To deal with items that don't yet exist in your dictionary, my personally preferred way is to use TryGetValue:

int stock;
inventory.TryGetValue(product, out stock);
inventory[product] = stock + 1;

This works because TryGetValue sets stock to default(int), which is 0, if the product does not yet exist. 0 is exactly the value you want.

If you prefer to treat the stock value as unassigned after TryGetValue returns false (for readability), then you can still use this same general approach:

int stock;
if (!inventory.TryGetValue(product, out stock))
  stock = 0;
inventory[product] = stock + 1;

Upvotes: 2

Michael0x2a
Michael0x2a

Reputation: 63978

Something like this?

myDictionary[myProduct] += stockIncrease;

It's pretty much exactly the syntax as you would use to update an item in an array.

If it helps, think of it less in terms of "I want to the stock to go up" and more in terms of "how do I get the value that I need, and what can I do with that value".

If it's not guaranteed whether or not your product exists in your dictionary to begin with, then just add on an if-check:

if (!inventory.ContainsKey(myProduct)) {
    inventory[myProduct] = 0;
}
inventory[myProduct] += stockIncrease;

Upvotes: 3

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