C#: Remove duplicate values from dictionary?

Question

How can I create a dictionary with no duplicate values from a dictionary that may have duplicate values?

IDictionary myDict = new Dicti         


        

Answer 1

What do you want to do with the duplicates? If you don't mind which key you lose, just build another dictionary like this:

IDictionary myDict = new Dictionary();

myDict.Add("1", "blue");
myDict.Add("2", "blue");
myDict.Add("3", "red");
myDict.Add("4", "green");

HashSet knownValues = new HashSet();
Dictionary uniqueValues = new Dictionary();

foreach (var pair in myDict)
{
    if (knownValues.Add(pair.Value))
    {
        uniqueValues.Add(pair.Key, pair.Value);
    }
}

That assumes you're using .NET 3.5, admittedly. Let me know if you need a .NET 2.0 solution.

Here's a LINQ-based solution which I find pleasantly compact...

var uniqueValues = myDict.GroupBy(pair => pair.Value)
                         .Select(group => group.First())
                         .ToDictionary(pair => pair.Key, pair => pair.Value);