C# 4 and .NET 4

Variables ❘ 29
Variable scope
The scope of a variable is the region of code from which the variable can be accessed. In general, the scope
is determined by the following rules:
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A field (also known as a member variable) of a class is in scope for as long as its containing class is
in scope.
A local variable is in scope until a closing brace indicates the end of the block statement or method
in which it was declared.
A local variable that is declared in a for, while, or similar statement is in scope in the body of
that loop.
scope Clashes for local Variables
It’s common in a large program to use the same variable name for different variables in different parts of the
program. This is fine as long as the variables are scoped to completely different parts of the program so that
there is no possibility for ambiguity. However, bear in mind that local variables with the same name can’t be
declared twice in the same scope. For example, you can’t do this:
int x = 20;
// some more code
int x = 30;
Consider the following code sample:
using System;
namespace Wrox.ProCSharp.Basics
{
public class ScopeTest
{
public static int Main()
{
for (int i = 0; i < 10; i++)
{
Console.WriteLine(i);
} // i goes out of scope here
// We can declare a variable named i again, because
// there's no other variable with that name in scope
}
}
}
for (int i = 9; i >= 0; i--)
{
Console.WriteLine(i);
} // i goes out of scope here.
return 0;
code snippet Scope.cs
This code simply prints out the numbers from 0 to 9, and then back again from 9 to 0, using two
for loops. The important thing to note is that you declare the variable i twice in this code, within the
same method. You can do this because i is declared in two separate loops, so each i variable is local to
its own loop.
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