Hi @Suresh S
You could use this way to call rest api and you could use DefaultCredentials to authenticate.
string url = "http://sp/_api/web/getfolderbyserverrelativeurl('/Document/Folder1')/files?$expand=ListItemAllFields";
HttpWebRequest webRequest = (HttpWebRequest)WebRequest.Create(url);
webRequest.AuthenticationLevel = System.Net.Security.AuthenticationLevel.MutualAuthRequested;
webRequest.Credentials = System.Net.CredentialCache.DefaultNetworkCredentials;
webRequest.Method = "GET";
Stream response = webRequest.GetResponse().GetResponseStream();
StreamReader reader = new StreamReader(response);
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