Which Class to create for a collection

Scott Stewart

I read the article at MSDN (http://msdn.microsoft.com/en-us/library/6tc79sx1.aspx) about selecting a collection class, but I don't understand any better. I am converting a VBA Access program to C#. I have a class that represents a document and the various parts of a document. I want to be able to add each document to a collection. In VBA it was difficult because you had to create a unique ID for each instance and then add it to the collection. So I created a class and the parameters. Do I have to create a unique ID for the collection? I want to be able to sort the members of the collection by a date. I want to be able to do a "For each" type of operation on the collection. There should not be a lot of work in the class since it is just an instrument that will eventually be put back into the database.
I am using "using System.Collections.Generic" with parameters such as public string Volume {get; set;}.
Be gentle with me. I have never used C# before! I have read a lot of stuff, but I still need some guidance.
Visual Studio Professional 10, Windows 7.
If you think I am going about this the wrong way please ask questions so I can better explain myself.

Thanks for the input!

Scott

3 Replies

Know the answer? Post it — somebody with the same question will find it here.

Vulpes14y ago
Accepted answer
You only need to create a unique ID for each document if you want to access them by that ID. You could then create a generic Dictionary with the ID as the key and the document object as the value.

However, it sounds to me like a generic List should suffice. This is basically a dynamic array - an array which increases its size automatically as new elements are added. Individual elements can be accessed in the same way as an array starting at index 0.

You can easily add the ability to sort your documents in any way you wish by implementing the generic IComparable interface.

You can also use foreach to iterate through the elements of the List.

The following simple example may help you to get going:

using System;
using System.Collections.Generic;

class Document : IComparable
{
public string Author {get; set;}
public string Title {get; set;}
public DateTime DatePublished {get; set;}

public Document(string author, string title, DateTime datePublished)
{
Author = author;
Title = title;
DatePublished = datePublished;
}

public override string ToString()
{
return String.Format("Author {0}, Title {1}, Date Published {2}", Author, Title, DatePublished.ToShortDateString());
}

public int CompareTo(Document other)
{
return this.DatePublished.CompareTo(other.DatePublished);
}
}

class Test
{
static void Main()
{
Document d1 = new Document("George Orwell", "Animal Farm", new DateTime(1945, 8, 17));
Document d2 = new Document("Leo Tolstoy", "War and Peace", new DateTime(1869, 1, 1));
Document d3 = new Document("Charles Dickens", "Bleak House", new DateTime(1852, 3, 1));

List documents = new List();
documents.Add(d1);
documents.Add(d2);
documents.Add(d3);

// iterate documents in order added to list
foreach(Document doc in documents) Console.WriteLine(doc);
Console.WriteLine();

documents.Sort();

// iterate documents in sorted order by date published
foreach(Document doc in documents) Console.WriteLine(doc);
Console.ReadKey();
}
}
Sam Hobbs14y ago
I am nearly certain that it can be done even easier without implementing IComparable. Since you already have an answer I won't go into details but you could create some other type of collection that has the DatePublished in a separate field. It might be a little less efficient but it would be easier for a beginner to understand.
Frogleg14y ago
You beat me to it Vulpes- but here's my example anyway