How to generically format a boolean to a Yes/No string?

The framework itself does not provide this for you (as far as I know). Translating true/false into yes/no does not strike me as more common than other potential translations (such as on/off, checked/unchecked, read-only/read-write or whatever).

I imagine that the easiest way to encapsulate the behavior is to make an extension method that wraps the construct that you suggest yourself in your question:

public static class BooleanExtensions
{
    public static string ToYesNoString(this bool value)
    {
        return value ? Resources.Yes : Resources.No;
    }
}

Usage:

bool someValue = GetSomeValue();
Console.WriteLine(someValue.ToYesNoString());