When working with C# programming, one of the most common interview questions and beginner confusions is the difference between Call by Value and Call by Reference. Understanding these concepts is crucial for writing efficient and bug-free .NET applications.
What is Call by Value in C#?
In Call by Value, a copy of the variable’s value is passed to the method. Changes made inside the method do not affect the original variable.
Example:
public void UpdateValue(int number)
{
number = number + 10;
}
int value = 5;
UpdateValue(value);
Console.WriteLine(value); // Output: 5
👉 Key Point: The original variable remains unchanged because only a copy is passed.
What is Call by Reference in C#?
In Call by Reference, the method receives a reference to the variable. This means any modification inside the method directly affects the original variable. In C#, this is achieved using the ref or out keyword.
Example with ref:
public void UpdateValue(ref int number)
{
number = number + 10;
}
int value = 5;
UpdateValue(ref value);
Console.WriteLine(value); // Output: 15
👉 Key Point: The original variable is modified since a reference is passed instead of a copy.
Call by Value vs Call by Reference in C#: Quick Comparison
| Feature | Call by Value | Call by Reference |
|---|---|---|
| Data Passed | Copy of variable | Reference of variable |
| Original Value Changed? | ❌ No | ✅ Yes |
| Keywords Used | None | ref, out |
| Performance | Slightly slower for large data | More efficient for large data |
Final Thoughts
Both Call by Value and Call by Reference in C# are essential concepts for every C# developer. Use Call by Value when you don’t want the method to change the original variable, and Call by Reference when you need the method to modify the original data.
Mastering these basics will make your C# programming skills stronger and help you tackle tricky .NET interview questions with confidence.
