In C#, how do you create and use a delegate instance in code?

Introduction / Context:
After understanding what a delegate is conceptually, the next step is to know how to declare and create delegate instances in C# code. This is a common interview topic because it connects the theory of delegates with practical syntax. Many modern C# features such as events and LINQ queries rely heavily on delegates and lambda expressions under the hood.

Given Data / Assumptions:

• We are writing C# code targeting the .NET runtime.
• We want to create a delegate instance that can call a method with a specific signature.
• The question focuses on the process of creating and using a delegate.

Concept / Approach:
Creating a delegate involves two main steps. First you declare the delegate type, which defines the method signature. Then you create instances of that type by assigning them compatible methods or lambda expressions. The compiler checks the signatures at compile time, which ensures type safety. After that you can invoke the delegate like a normal method, and it will call whatever method or methods it references.

Step-by-Step Solution:
Step 1: Declare a delegate type using the delegate keyword, for example public delegate int Calculator(int x, int y); This specifies the return type and parameters. Step 2: Implement one or more methods that match this signature, such as int Add(int x, int y) or int Multiply(int x, int y). Step 3: Create a delegate instance by assigning it a compatible method, for example Calculator calc = Add; or Calculator calc = new Calculator(Add); Step 4: Optionally assign a lambda expression instead of a named method, such as Calculator calc = (a, b) => a + b; which the compiler converts into a delegate instance. Step 5: Invoke the delegate like a method, for example int result = calc(5, 3); which calls the underlying Add method or lambda and returns the result.

Verification / Alternative check:
If you inspect the compiled code or use an IDE to navigate definitions, you will see that the delegate type is compiled into a sealed class derived from System.MulticastDelegate, with Invoke, BeginInvoke, and EndInvoke methods. At runtime, calling the delegate instance executes the target method. This matches the behaviour described in the steps and confirms that declaring a delegate type and assigning methods or lambdas is the correct way to create delegates in C#.

Why Other Options Are Wrong:
Option B is wrong because SQL Server stored procedures are database objects and do not declare C# delegates. Option C is incorrect because machine configuration files define application settings, not delegate types or method bindings. Option D is wrong because switching between debug and release builds changes optimisation and debug information, not whether delegates are generated automatically.

Common Pitfalls:
A common pitfall is forgetting that method signatures must match exactly, including return type and parameter types, leading to compile time errors. Another issue is manually declaring many custom delegate types when built in generic delegates such as Action and Func can simplify code. Developers can also confuse events and delegates; events are based on delegates but add additional access control. Practising simple examples of delegate creation helps build confidence before working with more advanced patterns like event handlers and LINQ queries.

Final Answer:
In C#, you create a delegate instance by declaring a delegate type with the delegate keyword and then instantiating it by assigning a compatible method or lambda expression, which you can later invoke like a normal method.