Reading stream twice?

Question

When I have uploaded an image from my website I need to do 2 things:

1. read the image dimensions
2. save the image to the database

the first th

Answer 1

Well, the simplest way is:

file.InputStream.Position = 0;

... 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.

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();

Answer 2

In addition to Jon's answer: If you have a StreamReader, there is no Position parameter - instead you need to access its BaseStream.

For this purpose you can use a little extension method:

public static void ResetStreamReader(this StreamReader sr, long position = 0)
{
    if (sr == null) return;
    sr.BaseStream.Position = position;
}

Put it inside your public static Extension class, then you can use it like so:

sr.ResetStreamReader();

Or you can pass the desired start position, if you want to start with a position > 0, for example if you want to skip headers when you read the stream again.