curl.exe –v –u user:pwd –XPOST –T "file1.txt" –H "Content-Type:text/plain" "http://example.com/xx/xx/xx/insert"

string url = "http://example.com/xx/xx/xx/insert";
string fileName = @"file1.txt";

var client = new WebClient();
client.Credentials = new NetworkCredential("user", "pwd");
client.Headers.Add("Content-Type", "text/plain");
byte[] responseBinary = client.UploadFile(url, "POST", fileName);
string response = Encoding.UTF8.GetString(responseBinary);