Книга: C# 2008 Programmer

MemoryStream

MemoryStream

Sometimes you need to manipulate data in memory without resorting to saving it in a file. A good example is the PictureBox control in a Windows Form. For instance, you have a picture displayed in the PictureBox control and want to send the picture to a remote server, say a Web Service. The PictureBox control has a Save() method that enables you to save the image to a Stream object.

Instead of saving the image to a FileStream object and then reloading the data from the file into a byte array, a much better way would be to use a MemoryStream object, which uses the memory as a backing store (which is more efficient compared to performing file I/O; file I/O is relatively slower).

The following code shows how the image in the PictureBox control is saved into a MemoryStream object:

//---create a MemoryStream object---
MemoryStream ms1 = new MemoryStream();
//---save the image into a MemoryStream object---
pictureBox1.Image.Save(ms1, System.Drawing.Imaging.ImageFormat.Jpeg);

To extract the image stored in the MemoryStream object and save it to a byte array, use the Read() method of the MemoryStream object:

//---read the data in ms1 and write to buffer---
ms1.Position = 0;
byte[] buffer = new byte[ms1.Length];
int bytesRead = ms1.Read(buffer, 0, (int)ms1.Length);

With the data in the byte array, you can now proceed to send the data to the Web Service. To verify that the data stored in the byte array is really the image in the PictureBox control, you can load it back to another MemoryStream object and then display it in another PictureBox control, like this:

//---read the data in buffer and write to ms2---
MemoryStream ms2 = new MemoryStream();
ms2.Write(buffer, 0, bytesRead);
//---load it in another PictureBox control---
pictureBox2.Image = new Bitmap(ms2);

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