What Are Some Unexpected Corner Cases in C# and .NET?

Unveiling the Unexpected: C# and .NET's Hidden Quirks

This article explores some surprising behaviors in C# and .NET, demonstrating the need for rigorous testing and careful consideration of edge cases.

One intriguing example involves string interning. Consider this code snippet:

<code class="language-csharp">string x = new string(new char[0]);
string y = new string(new char[0]);
Console.WriteLine(object.ReferenceEquals(x, y));</code>

Intuitively, one might anticipate False as the output. However, both x and y are interned as empty strings, leading to a surprising True result.

Another unexpected behavior arises with nullable types and the GetType() method. If T is a nullable type and all overridden methods (except GetType()) are implemented, calling GetType() on a boxed instance can throw a NullReferenceException.

<code class="language-csharp">static void Foo<T>() where T : new()
{
    T t = new T();
    // ...

    // This throws a NullReferenceException...
    Console.WriteLine(t.GetType());
}</code>

Furthermore, generic constraints where T is a reference type and requires a non-null value (T : class, new()) present a subtle challenge. Although the new() constraint aims to guarantee a non-null instance, this can be bypassed using indirection, for example, with a custom proxy attribute that returns null for newly created instances:

<code class="language-csharp">[MyFunnyProxy]
class MyFunnyType : ContextBoundObject { }</code>

These examples illustrate the potential for unexpected behavior within the C# and .NET frameworks. Thorough testing and a keen awareness of edge cases are crucial for robust and reliable application development.

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