.net - Creating a constant Dictionary in C#

Question

What is the most efficient way to create a constant (never changes at runtime) mapping of strings to ints?

I've tried using a const Dictionary, but that didn't work out.

I could implement a immutable wrapper with appropriate semantics, but that still doesn't seem totally right.

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For those who have asked, I'm implementing IDataErrorInfo in a generated class and am looking for a way to make the columnName lookup into my array of descriptors.

I wasn't aware (typo when testing! d'oh!) that switch accepts strings, so that's what I'm gonna use. Thanks!

Answer 1

Creating a truly compile-time generated constant dictionary in C# is not really a straightforward task. Actually, none of the answers here really achieve that.

There is one solution though which meets your requirements, although not necessarily a nice one; remember that according to the C# specification, switch-case tables are compiled to constant hash jump tables. That is, they are constant dictionaries, not a series of if-else statements. So consider a switch-case statement like this:

switch (myString)
{
   case "cat": return 0;
   case "dog": return 1;
   case "elephant": return 3;
}

This is exactly what you want. And yes, I know, it's ugly.