Call by Value vs. Call by Reference in C#

One of the most frequently asked interview questions in C# is:

👉 What is Call/Pass by Value vs. Call/Pass by Reference ❓

Many developers, especially beginners, often respond with:
❌ Primitive types are passed by value, and reference types are passed by reference.

⚠ This is a misconception!

In this blog, I’ll break down the real difference between Call by Value and Call by Reference in C# with clear explanations and examples. Let's dive in!

Call by Value in C#

By default, in .NET, everything (value types & reference types) is passed by value, unless explicitly stated otherwise.

How It Works
When you pass a variable by value, a copy of the original variable is passed. Any modifications made inside the method won’t affect the original variable.

Call by Reference in C#

To pass a variable by reference, you must explicitly use the ref or out keyword. This means the method receives a reference to the original variable instead of a copy, and changes will affect the original value.

Final Takeaways

✔ By default, everything in C# is passed by value, whether it’s a value type or reference type.
✔ To modify the original variable, you must use ref or out.
✔ Reference types are NOT automatically passed by reference. Their reference is passed by value unless explicitly stated otherwise.