c# - 我想使用 LoadAsync 和 MemoryStream 将数据库中的图像加载到图片框中

Question

我想将数据库中的图像异步加载到图片框中。我该怎么做？现在我有:

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.";

我想做的是:

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

我正在使用 MySQL 数据库和 visual studio 2010 C#

Answer 1

不要将字节加载到图像中，这会破坏你想要实现的目的......(注意这是将图像放入临时文件的快速方法...... . 这里有很多额外的注意事项，其中最重要的是在完成后删除临时文件)

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
    }
}

另见 LoadProgressChanged 事件