Tip: Asp.Net Request.InputStream is empty?

Recently I needed to post some json data from browser to web server. I used the following codes to read the input stream:

System.IO.StreamReader sr = new System.IO.StreamReader(Request.InputStream);
string json = sr.ReadToEnd();

There's one problem with the above codes, that is the json variable will hold empty string even though I am sure that data is posted to the web server. The resolution of the problem is to always set the stream position to 0. The resulting codes looks like this:

Request.InputStream.Position = 0; System.IO.StreamReader sr = new System.IO.StreamReader(Request.InputStream);
string json = sr.ReadToEnd();

Now with the first line of the codes, you will be able to get the stream data.