C# dictionaries ValueOrNull / ValueorDefault

Question

Currently I'm using

var x = dict.ContainsKey(key) ? dict[key] : defaultValue

I'd like some way to have dictionary[key] return null for nonexistant keys, so I could write something like

var x =  dict[key] ?? defaultValue;

this also winds up being part of linq queries etc. so I'd prefer one-line solutions.

Answer 1

You can use a helper method:

public abstract class MyHelper {
    public static V GetValueOrDefault<K,V>( Dictionary<K,V> dic, K key ) {
        V ret;
        bool found = dic.TryGetValue( key, out ret );
        if ( found ) { return ret; }
        return default(V);
    }
}

var x = MyHelper.GetValueOrDefault( dic, key );

Answer 2

With an extension method:

public static class MyHelper
{
    public static V GetValueOrDefault<K, V>(this Dictionary<K, V> dic, K key, V defaultVal)
    {
        V ret;
        bool found = dic.TryGetValue(key, out ret);
        if (found) { return ret; }
        return defaultVal;
    }
    void Example()
    {
        var dict = new Dictionary<int, string>();
        dict.GetValueOrDefault(42, "default");
    }
}