Tip: How to Find the Size of the HTTP Resource Being Fetched

See how to use the HttpWebRequest class in C# to determine the size of a file.

by Srinath MS

Jan 23, 2018

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There are cases in which we might want to warn the user before an attempt is made to download a large file, or we might simply be interested to know its size before downloading.

In C#, we use the HttpWebRequest class to download objects from an URL. We can set the request method to be of "Head" type and examine the response header "Content-Length" to determine the size of the object.

string url = "http://mydomain.com/FileStore/bigfile.zip";
var urlRequest = (HttpWebRequest)WebRequest.Create(url);
//Set the request.method to ???HEAD???
urlRequest.Method = "HEAD";

var urlResponse = urlRequest.GetResponse();
string contentLength = urlResponse.Headers.Get("Content-Length");
Messagebox.Show(int.Parse(contentLength).ToString());

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