(Mono C#) PayPal -- Get an OAuth 2.0 Access Token

Demonstrates how to send a request to get a PayPal OAuth2 access token. Sends an HTTP request equivalent to the following:

curl https://api.sandbox.paypal.com/v1/oauth2/token \
  -H "Accept: application/json" \
  -H "Accept-Language: en_US" \
  -u "Client-Id:Secret" \
  -d "grant_type=client_credentials"

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// Note: Requires Chilkat v9.5.0.64 or greater.

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

Chilkat.Rest rest = new Chilkat.Rest();

// Make the initial connection.
// A single REST object, once connected, can be used for many PayPal REST API calls.
// The auto-reconnect indicates that if the already-established HTTPS connection is closed,
// then it will be automatically re-established as needed.
bool bAutoReconnect = true;
bool success = rest.Connect("api.sandbox.paypal.com",443,true,bAutoReconnect);
if (success != true) {
    Debug.WriteLine(rest.LastErrorText);
    return;
}

// Duplicate this request:

// 	curl https://api.sandbox.paypal.com/v1/oauth2/token \
// 	  -H "Accept: application/json" \
// 	  -H "Accept-Language: en_US" \
// 	  -u "Client-Id:Secret" \
// 	  -d "grant_type=client_credentials"

rest.AddHeader("Accept","application/json");
rest.AddHeader("Accept-Language","en_US");

// For additional help on where to find  your client ID and API secret, see PayPal Client_ID and API_Secret
rest.SetAuthBasic("PAYPAL_REST_API_CLIENT_ID","PAYPAL_REST_API_SECRET");

rest.AddQueryParam("grant_type","client_credentials");

string responseStr = rest.FullRequestFormUrlEncoded("POST","/v1/oauth2/token");
if (rest.LastMethodSuccess != true) {
    Debug.WriteLine(rest.LastErrorText);
    return;
}

Debug.WriteLine(rest.LastRequestHeader);

// A sample response:

// 	{
// 	  "scope": "https://api.paypal.com/v1/payments/.* https://api.paypal.com/v1/vault/credit-card https://api.paypal.com/v1/vault/credit-card/.*",
// 	  "access_token": "EEwJ6tF9x5WCIZDYzyZGaz6Khbw7raYRIBV_WxVvgmsG",
// 	  "token_type": "Bearer",
// 	  "app_id": "APP-6XR95014BA15863X",
// 	  "expires_in": 28800
// 	}

Chilkat.JsonObject json = new Chilkat.JsonObject();
json.Load(responseStr);
json.EmitCompact = false;

// Check the response status code.  A 200 indicates success..
if (rest.ResponseStatusCode != 200) {
    Debug.WriteLine(json.Emit());
    Debug.WriteLine("Failed.");
    return;
}

// Given that the access token expires in approx 8 hours,
// let's record the date/time this token was created.
// This will allow us to know beforehand if the token
// is expired (and we can then fetch a new token).
Chilkat.CkDateTime dateTime = new Chilkat.CkDateTime();
bool bLocalTime = false;
int dtNow = dateTime.GetAsUnixTime(bLocalTime);
json.AppendInt("tokenCreateTimeUtc",dtNow);

// Examine the access token and save to a file.
Debug.WriteLine("Access Token: " + json.StringOf("access_token"));
Debug.WriteLine("Full JSON Response:");
Debug.WriteLine(json.Emit());

Chilkat.StringBuilder sbResponse = new Chilkat.StringBuilder();
sbResponse.Append(json.Emit());
bool bEmitBom = false;
sbResponse.WriteFile("qa_data/tokens/paypal.json","utf-8",bEmitBom);