读取流两次? [英] Reading stream twice?
问题描述
当我从我的网站上传图片时，我需要做两件事:
When I have uploaded an image from my website I need to do 2 things:
- 读取图像尺寸
- 将图片保存到数据库
我做的第一件事是将图像流读入 Image 对象，如下所示:
the first thing I do is reading the image stream into an Image object, like so:
var file = Request.Files["logo"];
Image FullsizeImage = Image.FromStream(file.InputStream);
接下来我要做的是将文件"对象保存到数据库(LINQ to SQL).但是，当我尝试将图像保存到数据库时，来自文件的流在流的末尾有它的位置，并且似乎没有数据存在.
the next thing I do is to save the "file" object to the database (LINQ to SQL). BUT, when I try to save the image to database, the stream from the file has it's postion at the end of the stream, and it seems no data is present.
我知道我应该如何重置流并将其放回位置 0，但是我该如何以最有效和最正确的方式做到这一点?
I know I should somwhow reset the stream and put it back into position 0, but how do I do that the most effiecent and correct way ?
推荐答案
嗯，最简单的方法是:
file.InputStream.Position = 0;
... 假设流支持搜索.但是，如果您不小心，这可能会对 Image 产生有趣的影响 - 因为它会保留对流的引用.
... assuming the stream supports seeking. However, That may do interesting things to the Image if you're not careful - because it will have retained a reference to the stream.
您最好将数据加载到一个字节数组中，然后如果您仍然需要，然后从中创建两个单独的 MemoryStream 对象.如果您使用 .NET 4，很容易将一个流复制到另一个:
You may be best off loading the data into a byte array, and then creating two separate MemoryStream objects from it if you still need to. If you're using .NET 4, it's easy to copy one stream to another:
MemoryStream ms = new MemoryStream();
Request.Files["logo"].InputStream.CopyTo(ms);
byte[] data = ms.ToArray();
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