The singleton pattern is one of the most known and easiest design patterns in software engineering. In simple words, a singleton is a class which only allows a single instance of itself to be created. There are various different ways to implement this pattern in C#. In this tutorial, I will show you how you can implement the singleton design pattern with minimum amount of code.
public class LoginForm
{
private static bool instance_flag = false;
// Private Constructor to block direct object creation
private LoginForm()
{ }
public static LoginForm instance()
{
if (instance_flag)
{
return null;
}
else
{
instance_flag = true;
return new LoginForm();
}
}
// Class Destructor to reset instance_flag
~LoginForm()
{
instance_flag = false;
}
}
Following C3 Console application shows how to use a singleton LoginForm class. The first object f1 is created properly while attempt to create second instance f2 will return null.
class Program
{
static void Main(string[] args)
{
LoginForm f1 = LoginForm.instance();
Console.WriteLine(f1);
LoginForm f2 = LoginForm.instance();
Console.WriteLine(f2);
Console.Read();
}
}
