我想从数据库中加载图像到使用LoadAsync和一个MemoryStream一个图片框 [英] I want to load image from the database into a picture box using LoadAsync and a MemoryStream

问题描述

我在数据库中的图像，我想要异步加载到图片框。我会怎么做呢？现在我有：

I have images in the database that I want to load asynchronously into a picture box. How would I do this? Right now I have:

byte[] byteBLOBData = new byte[0];
byteBLOBData = (byte[])ds.Tables["magazine_images"].Rows[c - 1]["image"];
MemoryStream stmBLOBData = new MemoryStream(byteBLOBData);
pictureBox1.Image = Image.FromStream(stmBLOBData);
pictureBox1.SizeMode = PictureBoxSizeMode.StretchImage;
labelMsg.Text = "Picture loaded successfully.";

和我想做的事：

pictureBox1.LoadAsync("What should I put here?");

我使用MySQL数据库和Visual Studio 2010的C＃

I'm using MySQL database and visual studio 2010 C#

推荐答案

不要字节加载到图像时，即会打败你想达到什么样的目的？（注意，这是一个快速-N -dirty获取图像到一个临时文件......在这里，而不是其中最重要的是删除，当你完成了临时文件有很多额外的考虑）

Don't load the bytes into the image, that'll defeat the purpose of what you're trying to achieve... (note this is a quick-n-dirty to get the image into a temporary file... there's a lot of additional considerations here, not the least of which would be to delete the temporary file when you're done)

byte[] byteBLOBData = (byte[])ds.Tables["magazine_images"].Rows[c - 1]["image"];
string tempImageFileName = Path.Combine(Path.GetTempPath(), Path.GetTempFileName() + ".jpg");
using( FileStream fileStream = new FileStream(tempImageFileName, FileMode.OpenOrCreate, FileAccess.ReadWrite) ) {
    using( BinaryWriter writer = new BinaryWriter(fileStream) ) {
        writer.Write(byteBLOBData);
    }
}

pictureBox1.LoadCompleted += LoadCompleted;
pictureBox1.WaitOnLoad = false;
pictureBox1.LoadAsync(tempImageFileName);

...

...

private static void LoadCompleted( object sender, AsyncCompletedEventArgs e ) {
    if( e.Error != null ) {
        // will get this if there's an error loading the file
    } if( e.Cancelled ) {
        // would get this if you have code that calls pictureBox1.CancelAsync()
    } else {
        // picture was loaded successfully
    }
}

也看到了 LoadProgressChanged 事件

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