C# abstract keyword

C# abstract keyword

In this tutorial, we would learn about abstract keyword in c# programming language.

abstract: This modifier indicates that thing being modified has a missing or incomplete implementation.

This modifier in C# language applies to the following :

  1. Class

  2. Method

  3. Properties

  4. Indexers

  5. Events

Abstract class

A class declared with abstract modifier is an abstract class.

  • abstract classes are intended to be a base class of other classes - the developer can not create an Object of an abstract class.

  • an abstract class can have both abstract methods ( methods with definition) and non-abstract methods (methods without definition).

  • As an object can not be created for an abstract class, a derived class must be created for an abstract class.

    public abstract class Asset {
        public abstract decimal BuyPrice { get; }
        public abstract decimal SellPrice { get; }
        public abstract decimal CalculateProfit();
    public class Stock : Asset {
        public override decimal BuyPrice => 100;
        public override decimal SellPrice => 150;
        public override decimal CalculateProfit() {
            return (SellPrice - BuyPrice);
  • An abstract class must provide implementation for all interface members

  • An abstract class that implements an interface might map the interface methods onto abstract methods.

      interface I {
          void M();
      abstract class C : I {
          public abstract void M();

Abstract methods / Properties

  • abstract method declaration doesn't provide any implementation.

      public abstract class Asset {
              public abstract decimal CalculateProfit();
  • An abstract method is implicitly a virtual method - base class must provide its implementation.

  • It is an error to use static or virtual modifiers in an abstract method declaration.

  • Abstract method declarations are only permitted in abstract classes.

  • Abstract properties behave like abstract methods, except for the differences in declaration and invocation syntax..

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