Abstract Classes

An abstract class can share code while requiring derived classes to fill in a method.

AbstractClasses.cs

using System;

abstract class Report
{
    public string Title { get; }

    protected Report(string title)
    {
        Title = title;
    }

    public abstract string Body();

    public string Summary()
    {
        return Title + ":" + Body();
    }
}

class CountReport : Report
{
    private readonly int count;

    public CountReport(string title, int count) : base(title)
    {
        this.count = count;
    }

    public override string Body()
    {
        return count + " items";
    }
}

class Program
{
    static void Main()
    {
        int count = ;
        Report report = new CountReport("daily", count);
        string summary = report.Summary();

        Console.WriteLine($"count={count}");
        Console.WriteLine($"summary={summary}");
    }
}

using System;

abstract class Report
{
    public string Title { get; }

    protected Report(string title)
    {
        Title = title;
    }

    public abstract string Body();

    public string Summary()
    {
        return Title + ":" + Body();
    }
}

class CountReport : Report
{
    private readonly int count;

    public CountReport(string title, int count) : base(title)
    {
        this.count = count;
    }

    public override string Body()
    {
        return count + " items";
    }
}

class Program
{
    static void Main()
    {
        int count = ;
        Report report = new CountReport("daily", count);
        string summary = report.Summary();

        Console.WriteLine($"count={count}");
        Console.WriteLine($"summary={summary}");
    }
}

using System;

abstract class Report
{
    public string Title { get; }

    protected Report(string title)
    {
        Title = title;
    }

    public abstract string Body();

    public string Summary()
    {
        return Title + ":" + Body();
    }
}

class CountReport : Report
{
    private readonly int count;

    public CountReport(string title, int count) : base(title)
    {
        this.count = count;
    }

    public override string Body()
    {
        return count + " items";
    }
}

class Program
{
    static void Main()
    {
        int count = ;
        Report report = new CountReport("daily", count);
        string summary = report.Summary();

        Console.WriteLine($"count={count}");
        Console.WriteLine($"summary={summary}");
    }
}

abstract class An abstract class can define shared behavior and abstract members.