Locking mechanism is needed for static functions?

Question

I have created a CommonUtils.cs file containing 5 static functions (So that I can just "copy" this .cs for other projects in Visual Studio since I develop different C# applications) along with that I have many source files.

Now, I have compiled my project to a DLL. This dll is hosted via IIS server as an application. Many customers use this dll to perform something, say they generate a report.

I have been informed that "static functions" must not be used generously in this context and they should be applied, a "locking" mechanism since without lock, multiple threads of a single instance of program or multiple instances of a program, both can behave unexpectedly. Is it true?

Answer 1

I have been informed that "static functions" must not be used generously in this context and they should be applied, a "locking" mechanism since without lock, multiple threads of a single instance of program or multiple instances of a program, both can behave unexpectedly. Is it true?

Let's break it piece by piece. What is a static class?

A static class is basically the same as a non-static class, but there is one difference: a static class cannot be instantiated. In other words, you cannot use the new keyword to create a variable of the class type. Because there is no instance variable, you access the members of a static class by using the class name itself.

How CLR treats a static class?

As is the case with all class types, the type information for a static class is loaded by the .NET Framework common language runtime (CLR) when the program that references the class is loaded. The program cannot specify exactly when the class is loaded. However, it is guaranteed to be loaded and to have its fields initialized and its static constructor called before the class is referenced for the first time in your program. A static constructor is only called one time, and a static class remains in memory for the lifetime of the application domain in which your program resides.

Now why we may need locking?

Basically, locking is needed when we have race conditions. When someone may read data that someone else may alter them in the same time. Two separate threads have access to a shared resource and there isn't any mechanism to prevent this. In order you take an answer to your question, you have at first to answer another question.

Does your static methods access shared resources and there might be any race condition? If that's true, then you need to use locking. Otherwise, it is not needed.

For further information about static classes, please have a look here. While if you need more information about thread synchronization techniques, please have a look here.

Answer 2

Functions are immutable so you don't need to synchronize when calling a function. Function parameters are mutable but each invocation has it's own local copy. No need to synchronize either.

Synchronization is required when multiple thread work on the same data and there is at least one writer. This is about any variable that is shared between threads. Care is required for static variables and any instance variable reachable by a static variables.