Dictionary ContainsKey and get value in one function

Question

Is there a way to call Dictionary<string, int> once to find a value for a key? Right now I'm doing two calls like.

if(_dictionary.ContainsKey("key") {
 int _value = _dictionary["key"];
}

I wanna do it like:

object _value = _dictionary["key"] 
//but this one is throwing exception if there is no such key

I would want null if there is no such key or get the value with one call?

Answer 1

You can use TryGetValue

int value;
bool exists = _dictionary.TryGetValue("key", out value);

TryGetValue returns true if it contains the specified key, otherwise, false.

Answer 2

The selected answer the correct one. This is to provider user2535489 with the proper way to implement the idea he has:

public static class DictionaryExtensions 
{
    public static TValue GetValue<TKey, TValue>(this IDictionary<TKey, TValue> dictionary, TKey key, TValue fallback = default(TValue))
    {
        TValue result;

        return dictionary.TryGetValue(key, out result) ? result : fallback;
    }
}

Which can then be used with:

Dictionary<string, int> aDictionary;
// Imagine this is not empty
var value = aDictionary.GetValue("TheKey"); // Returns 0 if the key isn't present
var valueFallback = aDictionary.GetValue("TheKey", 10); // Returns 10 if the key isn't present

Answer 3

this should probably do it,for your purposes. Like you asked in the question ,getting all in one go,null or the value,into an object:

object obj = _dictionary.ContainsKey("key") ? _dictionary["key"] as object : null;

or..

int? result = _dictionary.ContainsKey("key") ? _dictionary["key"] : (int?)null;

Answer 4

I suppose, you could do something like this (or write a much clearer extension method).

        object _value = _dictionary.ContainsKey(myString) ? _dictionary[myString] : (int?)null;

I'm not sure I'd be particularly happy using that though, by combining the null and your "Found" condition, I would have thought you're just shifting the problem to a null check slightly further down the line.