How IDisposable and Using Statements Work Together in C#

Introduction to IDisposable and Resource Management

Tim begins by describing IDisposable as a “powerful tool for ensuring proper resource management and safety for your application.” He explains that unmanaged resources — like database connections, file streams, or system handles — are not automatically cleaned up by the garbage collector.

In contrast, managed resources (like strings or regular C# objects) are automatically handled by the garbage collection process. The problem arises when a class directly interacts with unmanaged code or unmanaged resources such as OS-level memory or file handles — since these are outside of the .NET runtime’s control.

Tim emphasizes that if unmanaged resources are not explicitly released, they remain allocated, causing memory leaks and poor system performance. The IDisposable interface was designed to give developers a deterministic cleanup mechanism — a guaranteed way to clean up resources when an object’s lifetime ends.

Simulating Resource Usage

To demonstrate the need for cleanup, Tim creates a small console app containing a DemoResource class. The class has a DoWork() method that simulates opening and closing a database connection:

public class DemoResource
{
    public void DoWork()
    {
        Console.WriteLine("Opening Connection");
        Console.WriteLine("Doing Work");
        Console.WriteLine("Closing Connection");
    }
}

public class DemoResource
{
    public void DoWork()
    {
        Console.WriteLine("Opening Connection");
        Console.WriteLine("Doing Work");
        Console.WriteLine("Closing Connection");
    }
}

This represents a typical workflow involving unmanaged resources — such as establishing a connection to a database or writing to a file. The operations inside DoWork() simulate what would happen if we used unmanaged resources directly.

When Things Go Wrong — Resource Leaks

At around the 2-minute mark, Tim demonstrates what happens when the process doesn’t complete properly. He adds an exception to simulate an error during the operation:

throw new Exception("I broke");

throw new Exception("I broke");

When this exception occurs, the program never reaches the “Closing Connection” line — meaning the unmanaged resource remains open.

Tim recalls his early experiences where servers had to be rebooted every night because applications failed to close database connections. These unclosed connections would accumulate, consuming all available memory and sockets. This is a classic example of resource leaks due to missing or improper cleanup logic.

The Role of IDisposable

To fix this, Tim introduces the IDisposable interface, which defines the Dispose method. Implementing IDisposable tells .NET that this class has resources to release and defines how those should be released.

Tim adds : IDisposable to his class and implements the method:

public class DemoResource : IDisposable
{
    public void Dispose()
    {
        Console.WriteLine("Closing Connection via Dispose");
    }
}

public class DemoResource : IDisposable
{
    public void Dispose()
    {
        Console.WriteLine("Closing Connection via Dispose");
    }
}

The Dispose method serves as a dedicated place for resource cleanup, such as freeing unmanaged memory, closing file handles, or releasing database connections.

Tim explains that this Dispose method can be called automatically using a using statement, ensuring that cleanup happens reliably — even when exceptions occur.

Using Statements and Deterministic Cleanup

Tim clarifies that using can mean two different things in C#:

• Using directive — at the top of the file (e.g., using System;)

• Using statement — for resource cleanup

He demonstrates the latter:

using DemoResource demo = new DemoResource();
demo.DoWork();

using DemoResource demo = new DemoResource();
demo.DoWork();

At the end of this statement’s scope, the compiler automatically calls the Dispose method. This ensures deterministic cleanup — meaning the resource is freed immediately after use, rather than waiting for the garbage collector to finalize the object later.

This approach enhances application stability and memory usage efficiency by ensuring that all disposable objects are properly disposed of at the right time.

What Happens When an Exception Occurs

Tim reintroduces the exception and re-runs the demo. Even though the exception interrupts the normal flow, the output shows that Dispose() is still called:

Opening Connection
Doing Work
I broke
Closing Connection via Dispose

Opening Connection
Doing Work
I broke
Closing Connection via Dispose

This demonstrates that the using block guarantees cleanup even during failures. It’s equivalent to placing cleanup logic inside a finally block, but much cleaner and more readable.

This is the power of the C# IDisposable pattern — it ensures that any managed or unmanaged resources are properly released without requiring manual cleanup in every part of your code.

The Scope of Using and When Dispose Is Called

Tim then explores how scope affects disposal timing. When the using declaration ends, the compiler automatically inserts a call to Dispose().

He shows that if you place another line like:

Console.WriteLine("I'm done running Program.cs");

Console.WriteLine("I'm done running Program.cs");

after the using statement, that line will execute before Dispose() is called, since disposal happens when the current scope exits (such as the end of the method).

To make the disposal occur earlier, Tim wraps the code in a using block:

using (DemoResource demo = new DemoResource())
{
    demo.DoWork();
}
Console.WriteLine("I'm done running Program.cs");

using (DemoResource demo = new DemoResource())
{
    demo.DoWork();
}
Console.WriteLine("I'm done running Program.cs");

Now, the Dispose method executes before the final print statement, as the object goes out of scope at the end of the block.

This demonstrates deterministic resource cleanup, ensuring resources are released immediately when the code block finishes execution.

The Full Dispose Pattern (Extended Concept)

While Tim’s demo focuses on the basics, it leads naturally to the full C# Dispose pattern used in production code. This pattern allows safe cleanup of both managed and unmanaged resources, supports inheritance, and avoids double cleanup. The pattern typically looks like this:

public class BaseResource : IDisposable
{
    private bool disposed = false; // To detect redundant calls

    // Public dispose method
    public void Dispose()
    {
        Dispose(true);
        GC.SuppressFinalize(this);
    }

    // Protected virtual dispose method
    protected virtual void Dispose(bool disposing)
    {
        if (!disposed)
        {
            if (disposing)
            {
                // Dispose managed resources here
            }

            // Free unmanaged resources here
            disposed = true;
        }
    }
}

public class BaseResource : IDisposable
{
    private bool disposed = false; // To detect redundant calls

    // Public dispose method
    public void Dispose()
    {
        Dispose(true);
        GC.SuppressFinalize(this);
    }

    // Protected virtual dispose method
    protected virtual void Dispose(bool disposing)
    {
        if (!disposed)
        {
            if (disposing)
            {
                // Dispose managed resources here
            }

            // Free unmanaged resources here
            disposed = true;
        }
    }
}

Here’s what’s happening:

• Dispose(bool disposing) distinguishes between disposing managed objects (when disposing is true) and releasing unmanaged resources (always required).

• The disposing parameter helps prevent disposing of managed objects during finalization, when the garbage collector might have already reclaimed them.

• GC.SuppressFinalize(this) prevents the garbage collector from calling the finalizer once manual disposal is done.

• protected virtual void Dispose(bool disposing) allows derived classes to override disposal behavior using protected override void Dispose(bool disposing) for cascade dispose calls.

This ensures efficient resource management, prevents resource leaks, and provides safe cleanup logic for both managed and unmanaged resources.

Why Proper Cleanup Matters

Tim’s example highlights the importance of implementing the Dispose pattern correctly — not only to close database connections but also to handle unmanaged memory, file handles, and system resources gracefully. By implementing IDisposable and wrapping objects in using statements, you ensure that:

• Resources are released promptly

• Garbage collection doesn’t need to handle unmanaged resources

• Memory usage remains optimal

• Applications stay stable and efficient

Conclusion

As Tim summarizes in his video, the IDisposable interface and using statement work hand in hand to guarantee that cleanup happens automatically, even when exceptions occur.

By implementing the Dispose pattern, you gain full control over how your objects free their managed and unmanaged resources, while the using block ensures this process is triggered at the right moment — no matter what happens.

This combination forms the backbone of effective resource management in C#, ensuring stable, efficient, and leak-free applications.

“When you use IDisposable with a using statement, the Dispose method will always be called at the end of the scope — exception or not.” — Tim Corey

In short, understanding and implementing the C# IDisposable pattern is an essential step toward mastering resource cleanup, preventing leaks, and enhancing application stability.