Generic method declaration in C Sharp (C#) - Step-by-Step Execution

Concept Flow - Generic method declaration

Start method call

↓

Specify type parameter <T>

↓

Method body uses T

↓

Execute method with T

↓

Return result of type T

↓

End method call

The generic method starts by specifying a type parameter T, then uses T inside the method body, and finally returns a value of type T.

Execution Sample

C Sharp (C#)

public T Echo<T>(T input) {
    return input;
}

var result = Echo<int>(5);

This method returns the input value of any type T. Here, it is called with int and returns 5.

Execution Table

Step	Action	Type Parameter T	Input Value	Return Value
1	Call Echo<int>(5)	int	5	N/A
2	Enter method body	int	5	N/A
3	Return input	int	5	5
4	Assign return to result	int	N/A	5

💡 Method returns input value 5 of type int, execution ends.

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	Final
T	undefined	int	int	int	int
input	undefined	5	5	5	5
result	undefined	undefined	undefined	undefined	5

Key Moments - 3 Insights

Why do we write <T> after the method name?

The <T> declares a placeholder type that the method can use. This is shown in execution_table step 1 where T is set to int.

How does the method know what type T is?

When calling the method, we specify the type (like Echo<int>), so T becomes int as shown in variable_tracker after step 1.

What type does the method return?

It returns the same type T that was passed in, as seen in execution_table step 3 where return value is 5 of type int.

Visual Quiz - 3 Questions

Look at the execution_table, what is the type of T at step 2?

A string

B int

C undefined

D object

💡 Hint

Check the 'Type Parameter T' column at step 2 in execution_table.

At which step does the method return the input value?

A Step 3

B Step 2

C Step 1

D Step 4

💡 Hint

Look for 'Return input' action in execution_table.

If we call Echo<string>("hello"), what would be the return value type?

A int

B bool

C string

D object

💡 Hint

Refer to how T is set in variable_tracker and execution_table for int; string would behave similarly.

Concept Snapshot

Generic method declaration syntax:
public T MethodName<T>(T param) { ... }

- <T> declares a type placeholder.
- Method uses T as a type inside.
- Caller specifies T when calling.
- Method returns or uses values of type T.

Full Transcript

This example shows a generic method named Echo that takes a parameter of type T and returns it. When calling Echo<int>(5), the type parameter T becomes int. The method receives input 5, returns it, and the result is assigned to variable result. The execution table traces each step: calling the method, entering the body, returning the input, and assigning the result. Variables T, input, and result change accordingly. Key points include understanding the <T> syntax, how the type is specified at call time, and that the method returns the same type. The quiz questions check understanding of the type parameter and return value.