Using Statement

Using Statement
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using (Font font1 = new Font("Arial", 10.0f)) 
{
    byte charset = font1.GdiCharSet;
}

=>File and Font are examples of managed types that access unmanaged 

resources (in this case file handles and device contexts). 

There are many other kinds of unmanaged resources and class 

library types that encapsulate them. All such types must implement 

the IDisposable interface.

=>As a rule, when you use an IDisposable object, you should declare and 

instantiate it in a using statement. The using statement calls the 

Dispose method on the object in the correct way, and (when you use it as 

shown earlier) it also causes the object itself to go out of scope as 

soon as Dispose is called. Within the using block, the object is 

read-only and cannot be modified or reassigned.

=>The using statement ensures that Dispose is called even if an exception

 occurs while you are calling methods on the object. You can achieve the 

same result by putting the object inside a try block and then calling 

Dispose in a finally block; in fact, this is how the using statement is 

translated by the compiler. The code example earlier expands to the 

following code at compile time (note the extra curly braces to create 

the limited scope for the object)

{
 Font font1 = new Font("Arial", 10.0f);
 try
 {
    byte charset = font1.GdiCharSet;
 }
 finally
 {
    if (font1 != null)
        ((IDisposable)font1).Dispose();
  }
}