C# Sealed - c# - c# tutorial - c# net



What is sealed keyword in C# ?

  • C# sealed keyword applies restrictions on the class and method.
  • If you create a sealed class, it cannot be derived.
  • If you create a sealed method, it cannot be overridden.
learn c# tutorials - sealed class csharp in c#

learn c# tutorial - sealed class csharp in c# Example

Note: Structs are implicitly sealed therefore they can't be inherited.

C# Sealed class

  • C# sealed class cannot be derived by any class. Let's see an example of sealed class in C#.
using System;  

sealed public class Animal{  

public void eat() { Console.WriteLine("eating..."); }  

}  

public class Dog: Animal  

{  

public void bark() { Console.WriteLine("barking..."); }  

}  

public class TestSealed  

{  

public static void Main()  

{  

Dog d = new Dog();  
d.eat();  
d.bark();  


}  
}  
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C# examples - Output :

Compile Time Error: 'Dog': cannot derive from sealed type 'Animal'

C# Sealed method

  • The sealed method in C# cannot be overridden further. It must be used with override keyword in method.
  • Let's see an example of sealed method in C#.
using System;  
public class Animal{  
public virtual void eat() { Console.WriteLine("eating..."); }  
public virtual void run() { Console.WriteLine("running...");}  
}  
public class Dog: Animal  
{  
public override void eat() { Console.WriteLine("eating bread..."); }  
public sealed override void run() {   
Console.WriteLine("running very fast...");   
}  
}  
public class BabyDog : Dog  
{  
public override void eat() { Console.WriteLine("eating biscuits..."); }  
public override void run() { Console.WriteLine("running slowly..."); }  
}  
public class TestSealed  
{  
public static void Main()  
{  
BabyDog d = new BabyDog();  
d.eat();  
d.run();  
}  
}  
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C# examples - Output :

Compile Time Error: 'BabyDog.run()': cannot override inherited member 'Dog.run()' because it is sealed

Note: Local variables can't be sealed.

using System;  
public class TestSealed  
{  
public static void Main()  
{  
sealed int x = 10;  
x++;  
Console.WriteLine(x);  
}  
}  
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C# examples - Output :

Compile Time Error: Invalid expression term 'sealed'


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