How can you use optional parameters in C#?

Question

^{Note: This question was asked at a time when C# did not yet support optional parameters (i.e. before C# 4).}

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Answer 1

For a larger number of optional parameters, a single parameter of Dictionary could be used with the ContainsKey method. I like this approach because it allows me to pass a List or a T individually without having to create a whole other method (nice if parameters are to be used as filters, for example).

Example (new Dictionary() would be passed if no optional parameters are desired):

public bool Method(string ParamA, Dictionary AddlParams) {
    if(ParamA == "Alpha" && (AddlParams.ContainsKey("foo") || AddlParams.ContainsKey("bar"))) {
        return true;
    } else {
        return false;
    }
}