Advanced C# Topics

Welcome to the advanced section of C# documentation. Here, we delve into more complex and powerful features of the C# language that enable you to build robust, efficient, and scalable applications.

Reflection

Reflection allows you to inspect the metadata of types at runtime. This enables dynamic invocation of methods, accessing fields and properties, and even creating instances of types whose names are determined at runtime. It's a powerful tool for metaprogramming and building flexible frameworks.

Key aspects include:

• Type class for inspecting types.
• MethodInfo, PropertyInfo, FieldInfo for accessing members.
• Dynamic invocation of methods.

Attributes

Attributes provide a way to add declarative information to your code elements (classes, methods, properties, etc.). This metadata can be inspected at runtime using reflection and used by frameworks or libraries to alter behavior or provide additional information.

Common uses:

• [Serializable] attribute to mark types for serialization.
• [Obsolete] attribute to indicate deprecated members.
• Custom attributes for framework-specific behavior.

[AttributeUsage(AttributeTargets.Class | AttributeTargets.Method)]
public class MyCustomAttribute : Attribute
{
    public string Description { get; set; }
}

[MyCustomAttribute(Description = "This is a sample class.")]
public class MyClass
{
    [MyCustomAttribute(Description = "This is a sample method.")]
    public void MyMethod()
    {
        // Method implementation
    }
}
            

Expression Trees

Expression trees represent code as a data structure that can be traversed and manipulated. They are fundamental to LINQ providers and enable the translation of C# code into other query languages, such as SQL.

Key concepts:

• Building and compiling expression trees.
• Translating expression trees for remote execution.

Dynamic Language Runtime (DLR)

The DLR provides a common runtime environment for dynamic languages such as Python and Ruby, as well as for dynamic features within C#. It facilitates interoperability between dynamic and statically typed languages.

Features include:

• Dynamic objects.
• Expression trees as the backbone.
• Interoperability with other DLR-supported languages.

Advanced Asynchronous Programming

Beyond the basics of async and await, this section covers advanced patterns such as cancellation, timeouts, and handling complex asynchronous workflows. Optimizing asynchronous operations is crucial for responsive and scalable applications.

Topics include:

• CancellationTokenSource and CancellationToken.
• `Task.Delay` for timeouts.
• Advanced use cases of `Task.WhenAll`, `Task.WhenAny`.

Extension Methods

Extension methods allow you to add new methods to existing types without modifying their original source code. This is particularly useful for adding utility methods to types you don't own, such as types from the .NET framework.

public static class StringExtensions
{
    public static bool IsNullOrWhiteSpace(this string str)
    {
        return string.IsNullOrEmpty(str) || str.Trim().Length == 0;
    }
}

// Usage:
string myString = null;
bool isEmpty = myString.IsNullOrWhiteSpace(); // True
            

Advanced Generics

Explore advanced concepts in generics such as generic variance (covariance and contravariance), constraints on generic types, and how generics interact with other C# features.