C# Abstract Class and Interface Difference

In previous article you have learned about Interface and Abstract class in C#.

Now you learn the difference between abstract class and interface in C#.

Here are some of the key differences between interface and abstract class in C#.

Here we define one abstract class with some properties and methods.

public abstract class CarBaseClass
{
public string Color { get; set; }
abstract bool Start(); //Abstract cannot be private
public abstract bool Start();
bool Stop(); //either have body implementation or have abstract declaration
     bool Stop()
        {
            return true;
        }
}

Things to notice in above abstract class declaration

• Any abstract declaration must have a public access modifier, Abstract cannot be private
• We can have non abstract property/ method
• If we don’t define something as abstract, then we must have implementation (body)

Here is an example of how you can declare c# interface

public interface ICar
{
string Color { get; set; }
public bool Start(); //can't specify access modifier
bool Start();
void Stop()
{ } // can’t have implementation, only declaration
        void Stop();
    }

Things to notice in above interface declaration

• We can't specify any access modifier
• can’t have any body implementation, only declaration
• by default all members are override able, implementation must

You should read following tutorials to understand differences between C# abstract class and interface.

• C# Abstract Class Example
• C# Interface Example