Question

Is there a more concise way to check if x is either “a”,”b”,”c”,”d” or “e”?

if (x == "a" | x == "b" | x == "c" | x == "d" | x == "e"){//do something}

Basically I want to know if I can express the same if statement without repeating the variable name x.

Answer 1

How about:

string[] whiteList = { "a", "b", "c", "d", "e" };

if(whiteList.Contains(x))
{
    ...
}

You can consider using a HashSet<string> or similar and caching a reference to it in a field for improved performance (to give you an O(1) Contains operation and to avoid allocating, populating the collection).

//Field
HashSet<string> _whiteList = new HashSet<string> { "a", "b", "c", "d", "e" };

....

// In a method:
if(_whiteList.Contains(x))
{
    ...
}