Save structure in binary file and then read from it

Question

My program(in WinForms) is some kind of testing of some subject. I have such structure, where I save my questions of this test:

Dictionary<int, Question> questions = new Dictionary<int, Question>();

public class Question
{
    public Question(string q_text,  Dictionary<string, bool> ans)
    {
        text = q_text;
        answers = ans;
    }
    public string text { get; set; }
    public Dictionary<string, bool> answers { get; set; }       
}

I want to keep my questions(exactly Dictionary<int, Question> questions = new Dictionary<int, Question>();) in binary file and every time I start the program, it will read from this. I've never worked with binary files.

score 2 · Accepted Answer · edited Feb 19 '22 at 21:40

2

You can serialize the object and save it in a file. But you have to mark your class with [Serializable]

using System;
using System.Runtime.Serialization.Formatters.Binary;
using Microsoft.Build.Framework;
using Microsoft.Build.Utilities;

/// <summary>
/// Persists the object on HD
/// </summary>
public static void PersistObject()
{
    Logger.Debug("PersistObject: Started");
    // Persist to file
    FileStream stream = File.OpenWrite(_filePath);
    BinaryFormatter formatter = new BinaryFormatter();
    formatter.Serialize(stream, objectToSave);
    stream.Close();
    
    Logger.Debug("PersistObject: Ended");
}

/// <summary>
/// Loads the object.
/// </summary>
public static void LoadObject()
{
    try
    {
        Logger.Debug("LoadObject: Started");
        // Open file to read saved DailyUsers object
        if (File.Exists(_filePath))
        {
            FileStream stream = File.OpenRead(_filePath);
            BinaryFormatter formatter = new BinaryFormatter();
    
            object deserializedObject = formatter.Deserialize(stream);
            stream.Close();
        }
        Logger.Debug("LoadObject: Ended");
    }
    catch (Exception ex)
    {
        Logger.Error(ex, ex.Message);
    }
}

edited Feb 19 '22 at 21:40

Matt Kleinsmith

1,017
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answered Apr 21 '14 at 12:14

TamerM

722
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what library should I add for Logger? – user3528837 Apr 21 '14 at 13:09
Regret. I should use another method, because I need not to install new software for this task. – user3528837 Apr 21 '14 at 13:16
just ignore the Logger part. Its not necessary – TamerM Apr 21 '14 at 14:00
I should serialize every object of Question or can I just write into file Dictionary questions = new Dictionary()? And how to use LoadObject method? It doesn't return anything. – user3528837 Apr 21 '14 at 17:09
No just serialize the whole dictionary – TamerM Apr 21 '14 at 17:10
In the persist object method replace object to save variable with your questions dictionary. – TamerM Apr 21 '14 at 17:11
What's the problem there? You can handle it the way you want. Check if the object is null or save null. – TamerM Apr 21 '14 at 17:27
I managed to successfully write dictionary in bin file. Please, help me to Load it from file. I just don't understand your method, Can you explain it or rewrite for Dictionary? How to get Dictionary from file? – user3528837 Apr 21 '14 at 17:38
If you need further help feel free to comment here again – TamerM Apr 21 '14 at 18:13
`using System;` and `using System.Runtime.Serialization.Formatters.Binary;` – Matt Kleinsmith Feb 18 '22 at 23:05

yazan · Answer 2 · 2014-04-23T13:27:40.020

Well you can do that using serialization so check the following code:

   Dictionary<int, Question> questions = new Dictionary<int, Question>();

    [Serializable]
    public class Question
    {
        public Question(string q_text, Dictionary<string, bool> ans)
        {
            text = q_text;
            answers = ans;
        }
        public string text { get; set; }
        public Dictionary<string, bool> answers { get; set; }

        public static void Save(Question q,Stream st)
        {
            System.Runtime.Serialization.Formatters.Binary.BinaryFormatter bf =
                new System.Runtime.Serialization.Formatters.Binary.BinaryFormatter();

            bf.Serialize(st, q);

        }

        public static void SaveMany(Dictionary<int, Question> questions,Stream st)
        {
            System.Runtime.Serialization.Formatters.Binary.BinaryFormatter bf =
                new System.Runtime.Serialization.Formatters.Binary.BinaryFormatter();

            bf.Serialize(st, questions);

        }
        public static Question Load(Stream st)
        {
            System.Runtime.Serialization.Formatters.Binary.BinaryFormatter bf =
                new System.Runtime.Serialization.Formatters.Binary.BinaryFormatter();

            Question q = (Question)bf.Deserialize(st);

            return q;
        }
        public static Dictionary<int, Question> LoadMany(Stream st)
        {
            System.Runtime.Serialization.Formatters.Binary.BinaryFormatter bf =
                new System.Runtime.Serialization.Formatters.Binary.BinaryFormatter();

            Dictionary<int, Question> q = (Dictionary<int, Question>)bf.Deserialize(st);

            return q;
        }
    }

Can you also write an example, where you call these two functions. Cause, I am a bit confused. For example, I want to call Load function in Constructor. And method Save in the FinishButton_Click method. — user3528837, Apr 21 '14 at 12:56
Can I save just save Dictionary questions = new Dictionary() instead of every object? — user3528837, Apr 21 '14 at 17:15

score -1 · Answer 3 · edited May 23 '17 at 12:20

-1

You are wanting to serialize your objects using the BinaryFormatter class. This SO post will give you the code you need to accomplish this. But be aware that Dictionary<TKey, TValue> is NOT serializable, so you will not be serialize it directly. Instead, consider using List<KeyValuePair<int, Question>> to accomplish the same thing.

edited May 23 '17 at 12:20

Community

1
1

answered Apr 21 '14 at 12:15

Steve Danner

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7
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[`Dictionary`](http://msdn.microsoft.com/en-us/library/xfhwa508(v=vs.110).aspx) *is* serializable. – User 12345678 Apr 21 '14 at 12:17
Well, I stand SOMEWHAT corrected. You can serialize a `Dictionary` in binary format, but not to XML. I personally have run up against this in the past, which prompted my warning. Here is more detail on it, though: http://stackoverflow.com/questions/495647/serialize-class-containing-dictionary-member – Steve Danner Apr 21 '14 at 12:41

Save structure in binary file and then read from it

3 Answers3