Question

class operation
{
    public void add(int val1 , int val2)
    {
        int result;
        result= val1+ val2;
        return  result;
    }
}

class view : operation
{
    public override in  add(int val1 , int val2)
    {   
        int result;
        result = val1+val2;
        return result;
    }
}

Invalid token 'in' in class, struct, or interface member declaration

How can I remove this error from above code?

Answer 1

in is a reserved keyword in C#. You probably want:

public override int add(int val1, int val2)

Also in order to be able to override some method in a derived class this method must be virtual in the base class:

public class operation
{
    public virtual int add(int val1, int val2)
    {
        int result;
        result = val1 + val2;
        return result;
    }
}

In the operation base class you have declared the add method with no return type and yet you are trying to return an integer.

Also there’s no point in overriding a base method just to repeat the same code. You could simply invoke the base method in the overriden method:

public class view : operation
{
    public override int add(int val1, int val2)
    {
        return base.add(val1, val2);
    }
}

or simply:

public class view : operation
{
}

which would be equivalent because you are not modifying anything in this method.