find the union of two maps in csharp

To find the union of two maps (or dictionaries) in c#, we can use the Union method from the System.Linq namespace. The Union method returns a new map that contains all the keys and values from both input maps.

Here's a code snippet:

main.cs
using System.Linq;
using System.Collections.Generic;

Dictionary<string, int> map1 = new Dictionary<string, int>()
{
    { "a", 1 },
    { "b", 2 }
};

Dictionary<string, int> map2 = new Dictionary<string, int>()
{
    { "b", 3 },
    { "c", 4 }
};

Dictionary<string, int> unionMap = map1.Union(map2).ToDictionary(x => x.Key, x => x.Value);

// Output: { "a": 1, "b": 2, "c": 4 }
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In the above example, we first create two maps (map1 and map2) with some key-value pairs. Then we use the Union method to get a new map (unionMap) that contains all the keys and values from both map1 and map2. We then convert the resulting IEnumerable<KeyValuePair<string, int>> to a Dictionary using ToDictionary method.

The output of the example code will be a new dictionary with three key-value pairs: {"a": 1, "b": 2, "c": 4}. Note that the value for key "b" in map2 (3) is used instead of the value for the same key in map1 (2), because Union method picks the value from the second map if a key exists in both maps.