Variables Scope in C#

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Variables Scope in C#

The part of the program where a particular variable is accessible is termed as the Scope of that variable. A variable can be defined in a class, method, loop etc. In C/C++, all identifiers are lexically (or statically) scoped, i.e.scope of a variable can be determined at compile time and independent of the function call stack. But the C# programs are organized in the form of classes.

So C# scope rules of variables can be divided into three categories as follows:

  • Class Level Scope
  • Method Level Scope
  • Block Level Scope

Class Level Scope

  • Declaring the variables in a class but outside any method can be directly accessed anywhere in the class.
  • These variables are also termed as the fields or class members.
  • Class level scoped variable can be accessed by the non-static methods of the class in which it is declared.
  • Access modifier of class level variables doesn’t affect their scope within a class.
  • Member variables can also be accessed outside the class by using the access modifiers.
// C# program to illustrate the 
// Class Level Scope of variables 
using System; 

// declaring a Class 
class GFG { // from here class level scope starts 

	// this is a class level variable 
	// having class level scope 
	int a = 10; 

	// declaring a method 
	public void display() 
	{ 
		// accessing class level variable 
		Console.WriteLine(a); 

	} // here method ends 

} // here class level scope ends

Method Level Scope

  • Variables that are declared inside a method have method level scope. These are not accessible outside the method.
  • However, these variables can be accessed by the nested code blocks inside a method.
  • These variables are termed as the local variables.
  • There will be a compile-time error if these variables are declared twice with the same name in the same scope.
  • These variables don’t exist after method’s execution is over.

Example:

// C# program to illustrate the 
// Method Level Scope of variables 
using System; 

// declaring a Class 
class GFG { // from here class level scope starts 

	// declaring a method 
	public void display() 

	{ // from here method level scope starts 

		// this variable has 
		// method level scope 
		int m = 47; 

		// accessing method level variable 
		Console.WriteLine(m); 

	} // here method level scope ends 

	// declaring a method 
	public void display1() 

	{ // from here method level scope starts 

		// it will give compile time error as 
		// you are trying to access the local 
		// variable of method display() 
		Console.WriteLine(m); 

	} // here method level scope ends 

} // here class level scope ends

Block Level Scope

  • These variables are generally declared inside the for, while statement etc.
  • These variables are also termed as the loop variables or statements variable as they have limited their scope up to the body of the statement in which it declared.
  • Generally, a loop inside a method has three level of nested code blocks(i.e. class level, method level, loop level).
  • The variable which is declared outside the loop is also accessible within the nested loops. It means a class level variable will be accessible to the methods and all loops. Method level variable will be accessible to loop and method inside that method.
  • A variable which is declared inside a loop body will not be visible to the outside of loop body.

Example:

// C# code to illustrate the Block 
// Level scope of variables 
using System; 

// declaring a Class 
class GFG 

{ // from here class level scope starts 

	// declaring a method 
	public void display() 

	{ // from here method level scope starts 

		// this variable has 
		// method level scope 
		int i = 0; 

		for (i = 0; i < 4; i++) { 

			// accessing method level variable 
			Console.WriteLine(i); 
		} 

		// here j is block level variable 
		// it is only accessible inside 
		// this for loop 
		for (int j = 0; j < 5; j++) { 
			// accessing block level variable 
			Console.WriteLine(j); 
		} 

		// this will give error as block level 
		// variable can't be accessed outside 
		// the block 
		Console.WriteLine(j); 

	} // here method level scope ends 

} // here class level scope ends

Does C# support Global Variables?

C# is an object-oriented programming (OOP) language and does not support global variables directly. The solution is to add a static class containing the global variables. Using a global variable violates the OOP concept a bit, but can be very useful in certain circumstances.

Published by Zahid Hossain