(.NET Core C#) Dropbox Refresh OAuth2 Access Token

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Demonstrates how to mint a new access token using the refresh token obtained when originally getting the OAuth2 access token.

For more information, see https://www.dropbox.com/developers/documentation/http/documentation

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

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

// Implements the following CURL command:

// curl -X GET https://api.dropbox.com/oauth2/token \
//     -d grant_type=refresh_token \
//     -d refresh_token=<YOUR_REFRESH_TOKEN> \
//     -u <YOUR_APP_KEY>:<YOUR_APP_SECRET>

// Use the following online tool to generate HTTP code from a CURL command
// Convert a cURL Command to HTTP Source Code

http.Login = "DROPBOX_APP_KEY";
http.Password = "DROPBOX_APP_SECRET";

// Get the refresh token from the JSON we saved when originally getting the access token.
// (See Get Dropbox OAuth2 Access Token w/ Refresh Token
Chilkat.JsonObject json = new Chilkat.JsonObject();
success = json.LoadFile("qa_data/tokens/dropbox.json");
if (success == false) {
    Debug.WriteLine(json.LastErrorText);
    return;
}

Chilkat.HttpRequest req = new Chilkat.HttpRequest();
req.AddParam("grant_type","refresh_token");
req.AddParam("refresh_token",json.StringOf("refresh_token"));

Chilkat.HttpResponse resp = http.PostUrlEncoded("https://api.dropbox.com/oauth2/token",req);
if (http.LastMethodSuccess == false) {
    Debug.WriteLine(http.LastErrorText);
    return;
}

Chilkat.StringBuilder sbResponseBody = new Chilkat.StringBuilder();
resp.GetBodySb(sbResponseBody);

Chilkat.JsonObject jResp = new Chilkat.JsonObject();
jResp.LoadSb(sbResponseBody);
jResp.EmitCompact = false;

Debug.WriteLine("Response Body:");
Debug.WriteLine(jResp.Emit());

int respStatusCode = resp.StatusCode;
Debug.WriteLine("Response Status Code = " + Convert.ToString(respStatusCode));
if (respStatusCode >= 400) {
    Debug.WriteLine("Response Header:");
    Debug.WriteLine(resp.Header);
    Debug.WriteLine("Failed.");

    return;
}

// Sample JSON response:
// (Sample code for parsing the JSON response is shown below)

// {
//   "access_token": "sl.AC75WPYRqOi0mxcRqlimbV9FKHu04biz5qHwatG3MTgzFK7kLrGVlM9EgP4603tE7bWw0s1rMbTKiHsf37TUshPYvq-3r0qeBr_PrZIAibN8XOQicvboiOnqx6JrDekq-w8D-tE",
//   "token_type": "bearer",
//   "expires_in": 14400
// }

string access_token = jResp.StringOf("access_token");
Debug.WriteLine("New Access Token: " + access_token);

// Perhaps update our Dropbox JSON file with the new access token.
// (The existing refresh token does not change, and can be used over and over to mint new access tokens.)
json.UpdateString("access_token",access_token);

json.WriteFile("qa_data/tokens/dropbox.json");