Designing C# Interfaces: When to Use NotImplementedException

Implementing interfaces in C# is a fundamental skill, but developers often struggle with how to handle methods that are not ready or do not fit a specific implementation. This course teaches you how to navigate C# interface design decisions confidently. You will understand when throwing a NotImplementedException is a helpful temporary placeholder and when it signals a deeper architectural flaw in your codebase. You will learn to: 1. Understand the core purpose of NotImplementedException and its role during rapid prototyping; 2. Apply the Interface Segregation Principle (ISP) to avoid creating bloated interfaces; 3. Identify how throwing this exception can violate the Liskov Substitution Principle (LSP); 4. Explore modern C# alternatives, such as default interface methods and Null Object patterns; 5. Practice writing clean unit tests and mock objects that handle unimplemented members safely. You will start with foundational definitions of interfaces and exceptions, then progress through real-world scenarios, architectural principles, and modern C# design patterns. This course is designed for beginner to intermediate C# developers who want to improve their software design skills. No advanced architectural experience is required. Start reading today to build cleaner, more robust C# applications.