Prototype Pattern

Create new objects by copying an existing object (the prototype) instead of instantiating from scratch.

What problem it solves

When:

• object creation is expensive or complex
• you need many similar objects
• you want to avoid tight coupling to concrete classes

…you clone instead of new.

public class Document : ICloneable
{
    public string Title { get; set; }
    public List<string> Pages { get; set; }

    public object Clone()
    {
        // deep copy
        return new Document
        {
            Title = this.Title,
            Pages = new List<string>(this.Pages)
        };
    }
}

Usage

Document original = new Document
{
    Title = "Report",
    Pages = new List<string> { "Intro", "Body" }
};

Document copy = (Document)original.Clone();
copy.Title = "Report Copy";