CODEWITHSUNDEEP
c#serialization
maynull
maynull

Reputation: 2046

How to deserialize a binary file of lists and read it?

My goal is to serialize a list of new structs and save it to the same file repeatedly(For example, whenever the list has 5 structs, append the new structs to the same file). 

class Program
{
    static void Main(string[] args)
    {
        List<struct_realTime2> list_temp2 = new List<struct_realTime2>(100000);

        // ADD 5 new structs to list_temp2 
        for (int num = 0; num < 5; num++)
        {
            list_temp2.Add(new struct_realTime2 { indexNum = num,
                                                  currentTime = DateTime.Now.ToString("yyyy/MM/dd HH:mm:ss.ffffff"),
                                                  currentType = "type" });
        }

        // WRITE structs
        using (var fileStream = new FileStream("file.bin", FileMode.Append))
        {
            var bFormatter = new BinaryFormatter();

            foreach (struct_realTime2 stru in list_temp2)
            {
                bFormatter.Serialize(fileStream, stru);
            }

            list_temp2.Clear() // empty the list
        }

        // READ structs
        var list = new List<struct_realTime2>();
        using (var fileStream = new FileStream("file.bin", FileMode.Open))
        {
            var bFormatter = new BinaryFormatter();
            while (fileStream.Position != fileStream.Length)
            {
                list.Add((struct_realTime2)bFormatter.Deserialize(fileStream));
            }                
        }

        // PRINT OUT  structs in the file
        foreach (struct_realTime2 stru in list)
        {
            string content_struct = stru.indexNum.ToString() + ", " + stru.currentTime;
            Console.WriteLine(content_struct);
        }

        // WRITE list
        using (var fileStream = new FileStream("file_list.bin", FileMode.Append))
        {
            var bFormatter = new BinaryFormatter();

            bFormatter.Serialize(fileStream, list_temp2);
        }
    }
}

[Serializable]
public struct struct_realTime2
{
    public int indexNum { get; set; }
    public string currentTime { get; set; }
    public string currentType { get; set; }
}

< the result >
C:\Users\null\source\repos\ConsoleApp6\ConsoleApp6\bin\Debug>ConsoleApp6.exe
0, 2019-11-10 15:31:52.044207
1, 2019-11-10 15:31:52.047225
2, 2019-11-10 15:31:52.047225
3, 2019-11-10 15:31:52.047225
4, 2019-11-10 15:31:52.047225

C:\Users\null\source\repos\ConsoleApp6\ConsoleApp6\bin\Debug>ConsoleApp6.exe
0, 2019-11-10 15:31:52.044207
1, 2019-11-10 15:31:52.047225
2, 2019-11-10 15:31:52.047225
3, 2019-11-10 15:31:52.047225
4, 2019-11-10 15:31:52.047225
0, 2019-11-10 15:31:55.700680
1, 2019-11-10 15:31:55.703627
2, 2019-11-10 15:31:55.703627
3, 2019-11-10 15:31:55.703627
4, 2019-11-10 15:31:55.703627

It works fine if I append each struct to the file and read them. But I want to avoid appending each struct to the file using a loop, and just want to append the list itself to the file repeatedly and read the file.

It seems appending the list works because whenever I run the program, the size of file_list.bin doubles. But how can I read file_list.bin and make a new list with the structs in the file?

I'd appreciate it if I could get some code for that.

Upvotes: 0

Views: 284

Answers (1)

tmaj
tmaj

Reputation: 34987

CSV

If you want to append data to existing file I recommend using a csv style serialization.

BinaryFormatter

If you serialize a list (an array would be better) then the mirror of 

bFormatter.Serialize(fileStream, list_temp2.ToArray());

is 

var list = (struct_realTime2[])bFormatter.Deserialize(fileStream));

This may not work if you append new data to an existing file (as opposed to overwriting the file each time).

Upvotes: 2

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