What are finalizers in C#?

In C#, finalizers are special methods provided by the language for performing cleanup operations on objects just before they are garbage collected. A finalizer is also known as a "destructor." Finalizers are used to release unmanaged resources (such as file handles, database connections, or memory allocated outside the .NET runtime) associated with an object before it is removed from memory.

Here are some key points about finalizers in C#:

1. Syntax : A finalizer is defined using the tilde ('~') symbol followed by the class name. It has no access modifier or parameters. Finalizers cannot be overloaded or explicitly called.

   
   class MyClass
   {
       ~MyClass()
       {
           // Cleanup logic
       }
   }
   

   Execution Timing : Finalizers are not called deterministically. The garbage collector determines when to invoke finalizers based on its own scheduling algorithm. This means you cannot predict exactly when a finalizer will be executed.
2. Unmanaged Resource Cleanup : Finalizers are commonly used to release unmanaged resources that an object might be holding, ensuring that those resources are properly disposed of before the object is garbage collected.
3. Overhead and Performance : The use of finalizers can introduce performance overhead because objects with finalizers take an additional round of garbage collection to clean up. Objects without finalizers are collected more efficiently in the first garbage collection pass.
4. Suppression : Objects that do not have any unmanaged resources to clean up typically do not need finalizers. You can suppress the finalization process using the 'GC.SuppressFinalize()' method. This can improve performance.
5. IDisposable Interface : In cases where unmanaged resources are involved, it's often a better practice to implement the 'IDisposable' interface along with a finalizer. The 'IDisposable' pattern allows explicit resource cleanup and provides more control over the cleanup process.

   
   class MyDisposableClass : IDisposable
   {
       private bool disposed = false;
   
       public void Dispose()
       {
           Dispose(true);
           GC.SuppressFinalize(this);
       }
   
       protected virtual void Dispose(bool disposing)
       {
           if (!disposed)
           {
               if (disposing)
               {
                   // Release managed resources
               }
   
               // Release unmanaged resources
   
               disposed = true;
           }
       }
   
       ~MyDisposableClass()
       {
           Dispose(false);
       }
   }
   

Some of the points we need to remember about finalizers:

1. Finalizers are invoked automatically when an object of the class is being disposed or destroyed.
2. Finalizers are exclusive to classes and cannot be used within structures.
3. Each class can have only a single finalizer.
4. Finalizers cannot be inherited or overridden.
5. Modifiers are not permitted in the name of finalizers, and passing parameters to a finalizer is also disallowed.

In summary, finalizers in C# provide a mechanism for releasing unmanaged resources associated with objects before they are garbage collected. However, due to their non-deterministic nature and potential performance overhead, it's generally recommended to use the 'IDisposable' pattern along with finalizers only when dealing with unmanaged resources, and to rely on the garbage collector to manage memory and object cleanup for most scenarios.