C# 0 The Complete Reference

R

EMEMBER

R

EMEMBER

For clarity, the remaining namespace examples in this chapter show all namespaces 

required by a program within the same file. In real-world code, however, a namespace will often 

be defined in its own file, as the preceding example illustrates.

Namespaces Prevent Name Conflicts

The key point about a namespace is that names declared within it won’t conflict with 

similar names declared outside of it. For example, the following program defines two 

namespaces. The first is 

Counter

, shown earlier. The second is called 

Counter2

. Both 

contain classes called 

CountDown

, but because they are in separate namespaces, the two 

classes do not conflict. Also notice how both namespaces are specified within the same file. 

As just explained, a single file can contain multiple namespace declarations. Of course, 

separate files for each namespace could also have been used.

// Namespaces prevent name conflicts.

using System;

// Declare the Counter namespace.

namespace Counter {

  // A simple countdown counter.

  class CountDown {

    int val;

    public CountDown(int n) {

      val = n;

    }

    public void Reset(int n) {

      val = n;

    }

    public int Count() {

      if(val > 0) return val--;

      else return 0;

    }

  }

}

// Declare the Counter2 namespace.

namespace Counter2 {

  /* This CountDown is in the Counter2 namespace and

     does not conflict with the one in Counter. */

  class CountDown {

    public void Count() {

      Console.WriteLine("This is Count() in the " +

                        "Counter2 namespace.");

    }

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