C＃文件序列化错误

Question

Good day all

I am trying to teach myself how to do C# file serialization again after not looking at it for year. I seem to have an error in my code, but cannot seem to fix it or grasp the problem. It has to do with deserializing the objects and reading it into an array.

Here is my code:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.Serialization.Formatters.Binary;
using System.Runtime.Serialization;
using System.Text;
using System.Threading.Tasks;
using System.IO;

namespace Serializing_Files
{
    [Serializable]
    public class Dog
    {
        public string Name { get; set; }
        public string Breed { get; set; }
        public int Age { get; set; }
        public bool IsFemale { get; set; }

        public Dog(string Name, string Breed, int Age, bool IsFemale)
        {
            this.Name = Name;
            this.Breed = Breed;
            this.Age = Age;
            this.IsFemale = IsFemale;
        }

        public override string ToString()
        {
            string dogInfo;

            dogInfo = "Name: "+this.Name;
            return dogInfo;
        }
    }

    public static class DogsFile
    {
        public static BinaryFormatter BFormatter { get; set; }
        public static FileStream FStream { get; set; }
        public static void WriteDog(string FileName, Dog NewDog)
        {
            FStream = new FileStream(FileName, FileMode.Append, FileAccess.Write);
            BFormatter = new BinaryFormatter();
            BFormatter.Serialize(FStream, NewDog);
            Console.WriteLine("{0} has been written to the file.", NewDog.Name);
            FStream.Close();
        }

        public static Dog[] ReadDogs(string FileName)
        {
            FStream = new FileStream(FileName, FileMode.Open, FileAccess.Read);
            BFormatter = new BinaryFormatter();

            Dog[] DogArray = new Dog[FStream.Length];
            int i = 0;

            while (FStream.Position < FStream.Length)
            {
                DogArray[i] = (Dog)BFormatter.Deserialize(FStream); //line where error occurs
                Console.WriteLine("The file contans the following Dogs:");
                Console.WriteLine(DogArray[i].ToString());

                i++;
            }
            FStream.Close();
            return DogArray;
        }
    }

    class Program
    {
        static void Main(string[] args)
        {
            string filename = @"C:\Dogfile.ser";
            Dog[] allDogs = new Dog[3];

            allDogs[0] = new Serializing_Files.Dog("Scruffy", "Maltese", 3, true);
            DogsFile.WriteDog(filename, allDogs[0]);

            allDogs[1] = new Serializing_Files.Dog("Butch", "Bulldog", 1, false);
            DogsFile.WriteDog(filename, allDogs[1]);

            allDogs[2] = new Serializing_Files.Dog("Balo", "Chow Chow", 1, false);
            DogsFile.WriteDog(filename, allDogs[2]);

            DogsFile.ReadDogs(filename);
            Console.ReadLine();
        }
    }
}

I am receiving the following runtime error in line 60:

An unhandled exception of type 'System.Runtime.Serialization.SerializationException' occurred in mscorlib.dll

Additional information: The input stream is not a valid binary format. The starting contents (in bytes) are: 0B-5F-5F-42-61-63-6B-69-6E-67-46-69-65-6C-64-01-01 ...

I wrote this file using a combination of several tutorials, so I might have misunderstood something. Could someone please help me understand what I am doing wrong? I would be extremely grateful for any advice you might be able to offer.

A follow up question: I am using "FileMode.Append" when adding to the file. How would I make sure that the file exists in the first place? Should I run a line of code at the start using "FileMode.Create" separately, or is there a better practice approach that I could use?

Many thanks in advance!

Answer 1

Your code does not crash. Probably you created file with different objects (Maybe you added some properties afterwards) and now it cannot deserialize. Remove your file and launch your program again. File mode works fine. No need to change.

Another point is to serialize collection instead of writing objects one by one.

Answer 2

public static class DogsFile
{
    public static BinaryFormatter BFormatter { get; set; }
    public static FileStream FStream { get; set; }
    public static void WriteDog(string FileName, Dog[] NewDog)
    {
        FStream = new FileStream(FileName, FileMode.OpenOrCreate, FileAccess.Write);
        BFormatter = new BinaryFormatter();
        BFormatter.Serialize(FStream, NewDog);
        FStream.Close();
    }

    public static Dog[] ReadDogs(string FileName)
    {
        FStream = new FileStream(FileName, FileMode.Open, FileAccess.Read);
        BFormatter = new BinaryFormatter();
        var DogArray = (Dog[])BFormatter.Deserialize(FStream);
        FStream.Close();
        return DogArray;
    }
}

Answer 3

After some helpful suggestions from @Access Denied and @ZRT, here is the working code. Thanks guys!

using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.Serialization.Formatters.Binary;
using System.Runtime.Serialization;
using System.Text;
using System.Threading.Tasks;
using System.IO;

namespace Serializing_Files
{
    [Serializable]
    public class Dog
    {
        public string Name { get; set; }
        public string Breed { get; set; }
        public int Age { get; set; }
        public bool IsFemale { get; set; }

        public Dog(string Name, string Breed, int Age, bool IsFemale)
        {
            this.Name = Name;
            this.Breed = Breed;
            this.Age = Age;
            this.IsFemale = IsFemale;
        }

        public override string ToString()
        {
            string dogInfo;

            dogInfo = "Name: " + this.Name + Environment.NewLine + "Breed: " + this.Breed + Environment.NewLine + "Age: " + this.Age + Environment.NewLine;
            if (this.IsFemale)
            {
                dogInfo += "Gender: Female";
            }
            else
            {
                dogInfo += "Gender: Male";
            }
            dogInfo += Environment.NewLine;

            return dogInfo;
        }
    }

    public static class DogsFile
    {
        public static BinaryFormatter BFormatter { get; set; }
        public static FileStream FStream { get; set; }
        public static void WriteDog(string FileName, Dog[] NewDogs)
        {
            FStream = new FileStream(FileName, FileMode.Create, FileAccess.Write);
            BFormatter = new BinaryFormatter();
            BFormatter.Serialize(FStream, NewDogs);

            Console.WriteLine("The following dogs were written to the file:" + Environment.NewLine);

            for (int i = 0; i < NewDogs.Length; i++)
            {
                Console.WriteLine(NewDogs[i].ToString());
            }

            Console.WriteLine(Environment.NewLine);

            FStream.Close();
        }

        public static Dog[] ReadDogs(string FileName)
        {
            FStream = new FileStream(FileName, FileMode.Open, FileAccess.Read);
            BFormatter = new BinaryFormatter();
            var DogArray = (Dog[])BFormatter.Deserialize(FStream);

            Console.WriteLine("The file contains the following dogs:"+Environment.NewLine);

            for (int i = 0; i < DogArray.Length; i++)
            {
                Console.WriteLine(DogArray[i].ToString());
            }

            FStream.Close();
            return DogArray;
        }
    }

    class Program
    {
        static void Main(string[] args)
        {
            string filename = @"C:\Dogfile1.ser";
            Dog[] allDogs = new Dog[3];

            allDogs[0] = new Dog("Scruffy", "Maltese", 3, true);

            allDogs[1] = new Dog("Butch", "Bulldog", 1, false);

            allDogs[2] = new Dog("Balo", "Chow Chow", 1, false);

            DogsFile.WriteDog(filename, allDogs);

            DogsFile.ReadDogs(filename);

            Console.ReadLine();
        }
    }
}