Merging dictionaries in C#

Question

What\'s the best way to merge 2 or more dictionaries (Dictionary) in C#? (3.0 features like LINQ are fine).

I\'m thinking of a method signa

Answer 1

The party's pretty much dead now, but here's an "improved" version of user166390 that made its way into my extension library. Apart from some details, I added a delegate to calculate the merged value.

/// 

/// Merges a dictionary against an array of other dictionaries.
/// 
/// The type of the resulting dictionary.
/// The type of the key in the resulting dictionary.
/// The type of the value in the resulting dictionary.
/// The source dictionary.
/// A delegate returning the merged value. (Parameters in order: The current key, The current value, The previous value)
/// Dictionaries to merge against.
/// The merged dictionary.
public static TResult MergeLeft(
    this TResult source,
    Func mergeBehavior,
    params IDictionary[] mergers)
    where TResult : IDictionary, new()
{
    var result = new TResult();
    var sources = new List> { source }
        .Concat(mergers);

    foreach (var kv in sources.SelectMany(src => src))
    {
        TValue previousValue;
        result.TryGetValue(kv.Key, out previousValue);
        result[kv.Key] = mergeBehavior(kv.Key, kv.Value, previousValue);
    }

    return result;
}