Does C# support the use of static local variables?
c#, static
Solution
No, C# does not support this. You can come close with:
private static System.Text.RegularExpressions.Regex re =
new System.Text.RegularExpressions.Regex("\\(copy (\\d+)\\)$");
private static string AppendCopyToFileName(string f)
{
}
The only difference here is the visibility of 're'. It is exposed to the classm not just to the method.
The `re` variable will be initialized the first time the containing class is used in some way. So keep this in a specialized small class.
Problem
Related: How do I create a static local variable in Java? Pardon if this is a duplicate; I was pretty sure this would have been asked previously, and I looked but didn't find a dupe. Is it possible for me to create a static local variable in C#? If so, how? I have a static private method that is used rarely. the static method uses a Regular Expression, which I would like to initialize once, and only when necessary. In C, I could do this with a local static variable. Can I do this in C#? When I try to compile this code: ``` private static string AppendCopyToFileName(string f) { static System.Text.RegularExpressions.Regex re = new System.Text.RegularExpressions.Regex("\\(copy (\\d+)\\)$"); } ``` ...it gives me an error: error CS0106: The modifier 'static' is not valid for this item If there's no local static variable, I suppose I could approximate what I want by creating a tiny new private static class, and inserting both the method and the variable (field) into the class. Like this: ``` public class MyClass { ... private static class Helper { private static readonly System.Text.RegularExpressions.Regex re = new System.Text.RegularExpressions.Regex("\\(copy (\\d+)\\)$"); internal static string AppendCopyToFileName(string f) { // use re here... } } // example of using the helper private static void Foo() { if (File.Exists(name)) { // helper gets JIT'd first time through this code string newName = Helper.AppendCopyToFileName(name); } } ... } ``` Thinking about this more, using a helper class like this there would yield a bigger net savings in efficiency, because the Helper class would not be JIT'd or loaded unless necessary. Right?