reformatted code snippet here
var builder = new StringBuilder();
builder.Append("https://api.login.yahoo.com/oauth/v2/get_request_token");
builder.Append("?oauth_nonce=" + Guid.NewGuid().ToString());
builder.Append("&oauth_timestamp=" + ((DateTime.UtcNow.Ticks - new DateTime(1970, 1, 1).Ticks) / (1000 * 10000)).ToString());
builder.Append("&oauth_consumer_key={the key i was given}"); builder.Append("&oauth_signature_method=plaintex");
builder.Append("&oauth_signature={the consumer secret i was given}%26"); builder.Append("&oauth_version=1.0 ");
builder.Append("&xoauth_lang_pref=\"en-us\""); builder.Append("&oauth_callback=\"oob\"");
var httpWebRequest = (HttpWebRequest)WebRequest.Create(builder.ToString());
httpWebRequest.ContentType = "application/x-www-form-urlencoded ";
httpWebRequest.Method = "POST";