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

Got scared to see complex answers, being new to C#.

Here are some simple answers.
Merging d1, d2, and so on.. dictionaries and handle any overlapping keys ("b" in below examples):

Example 1

{
    // 2 dictionaries,  "b" key is common with different values

    var d1 = new Dictionary() { { "a", 10 }, { "b", 21 } };
    var d2 = new Dictionary() { { "c", 30 }, { "b", 22 } };

    var result1 = d1.Concat(d2).GroupBy(ele => ele.Key).ToDictionary(ele => ele.Key, ele => ele.First().Value);
    // result1 is  a=10, b=21, c=30    That is, took the "b" value of the first dictionary

    var result2 = d1.Concat(d2).GroupBy(ele => ele.Key).ToDictionary(ele => ele.Key, ele => ele.Last().Value);
    // result2 is  a=10, b=22, c=30    That is, took the "b" value of the last dictionary
}

Example 2

{
    // 3 dictionaries,  "b" key is common with different values

    var d1 = new Dictionary() { { "a", 10 }, { "b", 21 } };
    var d2 = new Dictionary() { { "c", 30 }, { "b", 22 } };
    var d3 = new Dictionary() { { "d", 40 }, { "b", 23 } };

    var result1 = d1.Concat(d2).Concat(d3).GroupBy(ele => ele.Key).ToDictionary(ele => ele.Key, ele => ele.First().Value);
    // result1 is  a=10, b=21, c=30, d=40    That is, took the "b" value of the first dictionary

    var result2 = d1.Concat(d2).Concat(d3).GroupBy(ele => ele.Key).ToDictionary(ele => ele.Key, ele => ele.Last().Value);
    // result2 is  a=10, b=23, c=30, d=40    That is, took the "b" value of the last dictionary
}

For more complex scenarios, see other answers.
Hope that helped.