Attribute Constructor foreach List Property

`List`, serialize

In C# programs we often need to read and write data from the disk. A List can be serialized—here we serialize (to a file) a List of objects.

Serialize notes

The next time the program runs, we get this List straight from the disk. We see an example of BinaryFormatter and its Serialize methods.

Example code

We see a "Lizard" class in C# code. This is the class we are going to serialize. The program includes the relevant namespaces at the top.

Here We see a class called Lizard, and it has 3 properties. These properties are publicly accessible.

Info The first constructor in the example accepts 3 values, a string, an int and a bool.

Note The Serializable attribute is specified right before the class definition.

Tip You can type "s" to write a List of classes to a file, and "r" to read in that same List.

Tip 2 When you press "s," a new List of Lizard objects is created. Five different Lizard objects are instantiated.

using System;
using System.Collections.Generic;
using System.IO;
using System.Runtime.Serialization.Formatters.Binary;

[Serializable()]
public class Lizard
{
    public string Type { get; set; }
    public int Number { get; set; }
    public bool Healthy { get; set; }

    public Lizard(string t, int n, bool h)
    {
        Type =    t;
        Number =  n;
        Healthy = h;
    }
}

class Program
{
    static void Main()
    {
        while(true)
        {
            Console.WriteLine("s=serialize, r=read:");
            switch (Console.ReadLine())
            {
                case "s":
                    var lizards1 = new List<Lizard>();
                    lizards1.Add(new Lizard("Thorny devil",                1, true));
                    lizards1.Add(new Lizard("Casquehead lizard",           0, false));
                    lizards1.Add(new Lizard("Green iguana",                4, true));
                    lizards1.Add(new Lizard("Blotched blue-tongue lizard", 0, false));
                    lizards1.Add(new Lizard("Gila monster",                1, false));

                    try
                    {
                        using (Stream stream = File.Open("data.bin", FileMode.Create))
                        {
                            BinaryFormatter bin = new BinaryFormatter();
                            bin.Serialize(stream, lizards1);
                        }
                    }
                    catch (IOException)
                    {
                    }
                    break;

                case "r":
                    try
                    {
                        using (Stream stream = File.Open("data.bin", FileMode.Open))
                        {
                            BinaryFormatter bin = new BinaryFormatter();

                            var lizards2 = (List<Lizard>)bin.Deserialize(stream);
                            foreach (Lizard lizard in lizards2)
                            {
                                Console.WriteLine("{0}, {1}, {2}", lizard.Type, lizard.Number, lizard.Healthy);
                            }
                        }
                    }
                    catch (IOException)
                    {
                    }
                    break;
            }
        }
    }
}s=serialize, r=read:
s
s=serialize, r=read:
r
Thorny devil, 1, True
Casquehead lizard, 0, False
Green iguana, 4, True
Blotched blue-tongue lizard, 0, False
Gila monster, 1, False
s=serialize, r=read:

Code notes

We call the Serialize method on the BinaryFormatter instance. This Serialize method receives the stream you want to write to, and also the object itself.

Detail We wrap the file IO code in a try-catch block. This is important because file IO frequently throws.

And The Stream is wrapped in a using block. The File.Open call attempts to open the new file for writing.

Deserialize

To deserialize, the code uses a Stream wrapped in a using-block. A new BinaryFormatter object is created, and it is used to get a new List.

Note The Deserialize method, which accepts the Stream as a parameter, is slow but also powerful.

Finally We write the List of Lizards it has read in from the file to the screen in a foreach-loop.

Summary