Save and load MemoryStream to/from a file

问题

I am serializing an structure into a MemoryStream and I want to save and load the serialized structure.

So, How to Save a MemoryStream into a file and also load it back from file?

回答1:

You may use MemoryStream.WriteTo or Stream.CopyTo (supported in framework version 4.5.2, 4.5.1, 4.5, 4) methods to write content of memory stream to another stream.

memoryStream.WriteTo(fileStream);

Update:

fileStream.CopyTo(memoryStream);
memoryStream.CopyTo(fileStream);

回答2:

Assuming that MemoryStream name is ms.

This code writes down MemoryStream to a file:

using (FileStream file = new FileStream("file.bin", FileMode.Create, System.IO.FileAccess.Write)) {
   byte[] bytes = new byte[ms.Length];
   ms.Read(bytes, 0, (int)ms.Length);
   file.Write(bytes, 0, bytes.Length);
   ms.Close();
}

and this reads a file to a MemoryStream :

using (MemoryStream ms = new MemoryStream())
using (FileStream file = new FileStream("file.bin", FileMode.Open, FileAccess.Read)) {
   byte[] bytes = new byte[file.Length];
   file.Read(bytes, 0, (int)file.Length);
   ms.Write(bytes, 0, (int)file.Length);
}

In .Net Framework 4+, You can simply copy FileStream to MemoryStream and reverse as simple as this:

MemoryStream ms = new MemoryStream();
using (FileStream file = new FileStream("file.bin", FileMode.Open, FileAccess.Read))
    file.CopyTo(ms);

And the Reverse (MemoryStream to FileStream):

using (FileStream file = new FileStream("file.bin", FileMode.Create, System.IO.FileAccess.Write))
    ms.CopyTo(file);

回答3:

The stream should really by disposed of even if there's an exception (quite likely on file I/O) - using clauses are my favourite approach for this, so for writing your MemoryStream, you can use:

using (FileStream file = new FileStream("file.bin", FileMode.Create, FileAccess.Write)) {
    memoryStream.WriteTo(file);
}

And for reading it back:

using (FileStream file = new FileStream("file.bin", FileMode.Open, FileAccess.Read)) {
    byte[] bytes = new byte[file.Length];
    file.Read(bytes, 0, (int)file.Length);
    ms.Write(bytes, 0, (int)file.Length);
}

If the files are large, then it's worth noting that the reading operation will use twice as much memory as the total file size. One solution to that is to create the MemoryStream from the byte array - the following code assumes you won't then write to that stream.

MemoryStream ms = new MemoryStream(bytes, writable: false);

My research (below) shows that the internal buffer is the same byte array as you pass it, so it should save memory.

byte[] testData = new byte[] { 104, 105, 121, 97 };
var ms = new MemoryStream(testData, 0, 4, false, true);
Assert.AreSame(testData, ms.GetBuffer());

回答4:

For anyone looking for the short versions:

var memoryStream = new MemoryStream(File.ReadAllBytes("1.dat"));

File.WriteAllBytes("1.dat", memoryStream.ToArray());

回答5:

The combined answer for writing to a file can be;

MemoryStream ms = new MemoryStream();    
FileStream file = new FileStream("file.bin", FileMode.Create, FileAccess.Write);
ms.WriteTo(file);
file.Close();
ms.Close();

回答6:

For loading a file, I like this a lot better

MemoryStream ms = new MemoryStream();
using (FileStream fs = File.OpenRead(file))
{
    fs.CopyTo(ms);
}

回答7:

Save into a file

Car car = new Car();
car.Name = "Some fancy car";
MemoryStream stream = Serializer.SerializeToStream(car);
System.IO.File.WriteAllBytes(fileName, stream.ToArray());

Load from a file

using (var stream = new MemoryStream(System.IO.File.ReadAllBytes(fileName)))
{
    Car car = (Car)Serializer.DeserializeFromStream(stream);
}

where

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

namespace Serialization
{
    public class Serializer
    {
        public static MemoryStream SerializeToStream(object o)
        {
            MemoryStream stream = new MemoryStream();
            IFormatter formatter = new BinaryFormatter();
            formatter.Serialize(stream, o);
            return stream;
        }

        public static object DeserializeFromStream(MemoryStream stream)
        {
            IFormatter formatter = new BinaryFormatter();
            stream.Seek(0, SeekOrigin.Begin);
            object o = formatter.Deserialize(stream);
            return o;
        }
    }
}

Originally the implementation of this class has been posted here

and

[Serializable]
public class Car
{
    public string Name;
}

回答8:

I use a Panel Control to add a image or even stream video, but you can save the image on SQL Server as Image or MySQL as largeblob. This code works for me a lot. Check it out.

Here you save the image

MemoryStream ms = new MemoryStream();
Bitmap bmp = new Bitmap(panel1.Width, panel1.Height);
panel1.DrawToBitmap(bmp, panel1.Bounds);
bmp.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg); // here you can change the Image format
byte[] Pic_arr = new byte[ms.Length];
ms.Position = 0;
ms.Read(Pic_arr, 0, Pic_arr.Length);
ms.Close();

And here you can load, but I used a PictureBox Control.

MemoryStream ms = new MemoryStream(picarr);
ms.Seek(0, SeekOrigin.Begin);
fotos.pictureBox1.Image = System.Drawing.Image.FromStream(ms);

Hope helps.

来源：https://stackoverflow.com/questions/8624071/save-and-load-memorystream-to-from-a-file

标签

file

stream

memorystream