C# & .NET 8 Architect Mastery

Dynamic Types & ExpandoObject: When and when not to use them

1 Views Updated 5/4/2026

Dynamic Programming in C#

The dynamic keyword tells the compiler: "Trust me, this method exists. Don't check it until the app is running." While powerful, it is also dangerous and can hide bugs.

1. ExpandoObject

This is a special class that acts like a dictionary but lets you use dot notation.

dynamic user = new ExpandoObject();
user.Name = "Sandeep"; // Created at runtime!
**Architect Tip:** This is incredibly useful for handling unstructured data from a NoSQL DB or an external API where the schema changes constantly.

2. DLR Overhead

Using `dynamic` uses the **Dynamic Language Runtime (DLR)**. It is much slower than static code and bypasses type safety. 99.9% of the time, you should use an Interface or a Class. Only use `dynamic` for COM Interop, legacy interop, or extremely fluid data structures.

4. Interview Mastery

Q: "What is the difference between `object`, `var`, and `dynamic`?"

Architect Answer: "`object` is the base type; you need to cast it to use it. `var` is static typing where the compiler guesses the type for you (type-safe). `dynamic` is 'Delayed Typing' where no checks are done until runtime. `var` is for convenience; `dynamic` is for flexibility."

C# & .NET 8 Architect Mastery
1. Memory Management & Performance
The CLR Deep Dive: Stack, Heap, and Garbage Collection (GC) Value Types vs Reference Types: Structs, Records, and Classes Span<T> and Memory<T>: Zero-copy high-performance code Benchmarking with Benchmark.DotNet: Measuring nano-seconds
2. Advanced Asynchronous Programming
Async/Await Internals: The State Machine and TaskContext ValueTask vs Task: Avoiding allocation in hot paths Task.WhenAll vs Parallel.ForEachAsync: Concurrency at scale Thread Safety & Multi-threading: Locks, Semaphores, and Interlocked
3. Modern C# 12+ Features
Primary Constructors & Collection Expressions Pattern Matching: Switch expressions and Recursive patterns Required Members & Init-Only properties Native AOT (Ahead of Time): Deployment for serverless/edge
4. Enterprise Design Patterns in .NET
Dependency Injection (DI): Lifetime management and Captive Dependencies The Options Pattern: Type-safe configuration management The Factory & Builder Patterns in Modern .NET Middleware Architecture: Building custom ASP.NET Core pipelines
5. Dynamic Programming & Reflection
Reflection & Attributes: Building custom frameworks Expression Trees: Building dynamic LINQ queries Source Generators: Compile-time code generation for speed Dynamic Types & ExpandoObject: When and when not to use them
6. Testing & Quality Architecture
Unit Testing Patterns: xUnit, Moq, and FluentAssertions Integration Testing with WebApplicationFactory Mutation Testing: Testing the quality of your tests TDD (Test Driven Development) for Senior Architects
7. Modern Web API Architectures
Minimal APIs vs Controllers: Choice of architecture Rate Limiting & Throttling in ASP.NET Core Versioning Strategies: URL vs Header vs Media Type Real-time Web with SignalR and WebSockets
8. FAANG .NET Architect Interview
Case Study: Designing a High-Throughput Payment Gateway in .NET Case Study: Solving Memory Leaks and CPU Spikes in Production