Is Using `using` and `IDisposable` for State Management in C# an Abuse?

Using IDisposable for State Management

In C , a common pattern involves using the constructor and destructor of class A to handle entry and exit conditions for class B, ensuring a known state upon leaving the scope. This is not pure RAII, but an established practice.

In C#, a similar approach can be used with using and IDisposable. However, this usage raises a question:

Question: Is it abusive to use using and IDisposable as a means of obtaining "scoped behavior" for exception safety?

Answer:

Some opinions consider this usage of using and IDisposable to be an abuse. Here are the reasons:

• Misleading Intent: using is typically used for managing resources and disposing of them when no longer needed. Altering program state is not resource management, thus using using for this purpose misleads the reader.
• Unexpected Necessity: using should be used for convenience and not necessity. In this case, using using makes it appear as if a simple politeness mechanism is being used to mutate program state.
• Hidden Semantic Impact: Code analysis becomes challenging when using is used for state management, obscuring the true semantic impact of closing the using block.

For example, consider the following code:

{
    // Unlock the frobble
    this.Frobble.Unlock();

    try
    {
        // May throw
        Foo();
        this.Frobble.Fiddle();
        Bar();
    }
    finally
    {
        // Lock the frobble
        this.Frobble.Lock();
    }
}

This code is vulnerable to the problem that an exception thrown after the unlock but before entering the try block will leave the frobble unlocked. Using using to handle this state change would make this vulnerability more difficult to detect.

Therefore, it is generally recommended to use using for its intended purpose of resource management and to avoid using it for state management.

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