Exception Handling & Resource Disposal (IDisposable)

try-catch-finally, using declarations, and deterministic cleanup

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While the garbage collector manages memory, unmanaged resources (database connections, file handles, sockets) must be deterministically released using IDisposable and using.

The using Declaration and Exception Handling

using var stream = File.OpenRead(...);: Automatically calls .Dispose() the microsecond the containing scope exits.

try...catch (Exception ex) when (condition): C# supports exception filters to catch errors only when a boolean condition is satisfied.

Modern using Declaration Pattern

Try It Yourself »

public void ProcessLogs(string path) {
    // using declaration: Disposed automatically at the end of the method!
    using var reader = new StreamReader(path);
    
    string? line;
    while ((line = reader.ReadLine()) != null) {
        if (line.Contains("ERROR")) {
            Console.WriteLine($"Alert: {line}");
        }
    }
} // reader.Dispose() called here deterministically!

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Test Yourself With Exercise

+15 XP

What interface must a C# class implement to be eligible for deterministic resource cleanup via the `using` statement?

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