In C#, you can create private constructors. It is used in a class that contains static members only. You can NOT instantiate from a class that has a private constructor with the same parameters. The main purpose of a private constructor is to restrict the class from being instantiated. Take a look at the following class:
public class BaseClass
{
private BaseClass()
{
}
}
If you try to instantiate the above class, you will get the following error:
BaseClass baseClass=new BaseClass(); //'BaseClass.BaseClass()' is inaccessible due to its protection level [PrivateConstructor]
But you can have another public or private constructor in the same class:
public class BaseClass
{
private BaseClass()
{
}
public BaseClass(string a)
{
A = a;
}
public static string A { get; set; }
}
Another usage of the private constructor is when It is used in singleton design patterns, to make sure that only one instance of a class can be created.
private static BaseClass instance = null;
public static BaseClass getInstance()
{
if (instance == null)
{
instance = new BaseClass();
}
return instance;
}
Now, what’s the difference between creating a class with a private constructor and defining it as sealed!?