(.NET Core C#) Refresh a Dynamics CRM OAuth2 Access Token

Demonstrates how to refresh an expiring Dynamics CRM access token using the refresh token. endpoint.

(If a REST API call fails with a 401 unauthorized error, an application can auto-recover by refreshing the access token, and then re-send the request using the new token.)

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//  This example requires the Chilkat API to have been previously unlocked.
//  See Global Unlock Sample for sample code.

//  We previously obtained an access token and saved the JSON to a file using this example:
//  Get Dynamics CRM OAuth2 Access Token

//  This example will examine the JSON and expiration date, and if near expiration will
//  refresh the access token.

Chilkat.JsonObject json = new Chilkat.JsonObject();
bool success = json.LoadFile("qa_data/tokens/dynamicsCrm.json");
if (success != true) {
    return;
}

//  The contents of the JSON look like this:
//  {
//    "token_type": "Bearer",
//    "scope": "user_impersonation",
//    "expires_in": "3599",
//    "ext_expires_in": "0",
//    "expires_on": "1524783438",
//    "not_before": "1524779538",
//    "resource": "https://mydomain.api.crm.dynamics.com",
//    "access_token": "...",
//    "refresh_token": "...",
//    "id_token": "..."
//  }

//  The "expires_on" value is a Unix time.
Chilkat.CkDateTime dtExpire = new Chilkat.CkDateTime();
dtExpire.SetFromUnixTime(false,json.IntOf("expires_on"));

//  If this date/time expires within 10 minutes of the current system time, refresh the token.

//  OK, we need to refresh the access token by sending a POST...
// 

Chilkat.HttpRequest req = new Chilkat.HttpRequest();
req.AddParam("grant_type","refresh_token");
req.AddParam("redirect_uri","http://localhost:3017/");
req.AddParam("client_id","DYNAMICS-CRM-CLIENT-ID");
req.AddParam("client_secret","DYNAMICS-CRM-SECRET-KEY");
req.AddParam("refresh_token",json.StringOf("refresh_token"));
req.AddParam("resource","https://mydynamicsdomain.api.crm.dynamics.com");

Chilkat.Http http = new Chilkat.Http();

Chilkat.HttpResponse resp = http.PostUrlEncoded("https://login.microsoftonline.com/DYNAMICS-ENDPOINT-GUID/oauth2/token",req);
if (http.LastMethodSuccess != true) {
    Debug.WriteLine(http.LastErrorText);
    return;
}

//  Load the JSON response.
json.Load(resp.BodyStr);
json.EmitCompact = false;

//  Show the JSON response.
Debug.WriteLine(json.Emit());

Debug.WriteLine("Response status code: " + Convert.ToString(resp.StatusCode));

//  If the response status code is not 200, then it's an error.
if (resp.StatusCode != 200) {
    return;
}

//  If an "expires_on" member does not exist, then add the JSON member by
//  getting the current system date/time and adding the "expires_in" seconds.
//  This way we'll know when the token expires.
if (json.HasMember("expires_on") != true) {
    dtExpire.SetFromCurrentSystemTime();
    dtExpire.AddSeconds(json.IntOf("expires_in"));
    json.AppendString("expires_on",dtExpire.GetAsUnixTimeStr(false));
}

//  Save the refreshed access token JSON to a file for future requests.
Chilkat.FileAccess fac = new Chilkat.FileAccess();
fac.WriteEntireTextFile("qa_data/tokens/dynamicsCrm.json",json.Emit(),"utf-8",false);