C# Scope of Variables
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.
Example:
// 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
