Error: (401) Unauthorized access to httpwebrequest.

On a webpage, I don't want to log on to the interface and access it directly using the domain account password. If the website is set to window authentication, there is no problem on a separate page, but access through the httpwebrequest object will cause an error:
The remote server returns an error: (401) unauthorized.

Later find the ProcessingCodeThe code before processing is as follows:
Httpwebrequest HWR = (httpwebrequest) webrequest. Create (Surl + "shipworkflow. ashx ");
HWR. method = "get ";
HWR. sendchunked = false;

The code after processing is as follows:
Httpwebrequest HWR = (httpwebrequest) webrequest. Create (Surl + "shipworkflow. ashx ");
HWR. preauthenticate = true;
Networkcredential mycred = new networkcredential ("user", "1234", "ABC ");
HWR. Credentials = mycred;
HWR. method = "get ";
HWR. sendchunked = false;