PayPal: Create and Capture Order - asp.net-mvc

Question

I am following this sample (https://developer.paypal.com/docs/checkout/reference/server-integration/set-up-transaction/#on-the-server) to get PayPal working on the server.
I have finished creating the order, but it doesn't capture the order at the same time. Is it possible to create and capture the order at the same time?
var request = new OrdersCreateRequest();
request.Prefer("return=representation");
request.RequestBody(BuildRequestBody());
var response = await PayPalClient.client().Execute(request); //this will only create the order. How to capture it at the same time?
When I tried to capture the order:
//continue from above
var result = response.Result<Order>();
var requestCapture = new OrdersCaptureRequest(result.Id);
requestCapture.Prefer("return=representation");
requestCapture.RequestBody(new OrderActionRequest());
response = await PayPalClient.Client().Execute(requestCapture);
I get the error:
"name":"UNPROCESSABLE_ENTITY",
"details": [{
"issue":"ORDER_NOT_APPROVED",
"description":"Payer has not yet approved the Order for payment. Please redirect the payer to the 'rel':'approve' url returned as part of the HATEOAS links within the Create Order call or provide a valid payment_source in the request."
}],
"message": "The requested action could not be performed, semantically incorrect, or failed business validation.",
"links": [{
"href": "https://developer.paypal.com/docs/api/orders/v2/#error-ORDER_NOT_APPROVED",
"rel": "information_link",
"method": "GET"
}]
My question is, is it possible to create order, authorize and capture at the same time?
Thanks

Answer 1

Before using OrdersCaptureRequest, you have to redirect to [rel] => approve link from the response of OrdersCreateRequest:
$client = PayPalClient::client();
$response = $client->execute($request);
$res_links = $response->result->links;
$approve_index = array_search('approve',array_column($res_links,'rel'));
redirect($res_links[$approve_index]->href,'location',302);`
And then use OrdersCaptureRequest.

Answer 2

I don't think there's a way to create, authorize and capture order at the same time in PayPal, even in sandbox environment. You'll have to follow each step separately.
And about the ORDER_NOT_APPROVED error, you can either get the order approved by the user as #raj-kamal said, or you can make a Paypal-Auth-Assertion and send it in the headers. This header is an API client-provided JSON Web Token (JWT) assertion that identifies the merchant.
Reference: https://developer.paypal.com/docs/api/reference/api-requests/#paypal-auth-assertion
NOTE:
To use this header, you must get consent to act on behalf of a merchant.