C#でファイルをPUT送信する

using System.Net; を書いておかないとダメです。

// ファイルを開く
using (FileStream stream = new FileStream("C:\\test.txt", FileMode.Open, FileAccess.Read)) {
    // PUTでstream送信する
    HttpWebRequest request = (HttpWebRequest)WebRequest.Create("http://api.example.com/upload/");
    request.Method = "PUT";
    request.ContentType = "application/octet-stream";
    request.ContentLength = stream.Length;
    request.AllowWriteStreamBuffering = false;
    // タイムアウト6h
    request.Timeout = 360 * 60 * 1000;
    request.ReadWriteTimeout = 360 * 60 * 1000;
    try {
        using (Stream requestStream = request.GetRequestStream()) {
            stream.CopyTo(requestStream);
        }
    } catch (Exception) {
        // nop
    }
    request.GetResponse();
}