1. Create a new web experience profile. You can reuse the ID returned from this call with each PayPal payment, so you should only need to do this once. 
    

// Create the payment
var payment = new Payment
{
    intent = "sale",
    experience_profile_id = createdProfile.id,
    payer = new Payer
    {
        payment_method = "paypal"
    },
    transactions = new List<Transaction>
    {
        new Transaction
        {
            description = "Ticket information.",
            item_list = new ItemList
            {
                items = new List<Item>
                {
                    new Item
                    {
                        name = "Concert ticket",
                        currency = "USD",
                        price = "20.00",
                        quantity = "2",
                        sku = "ticket_sku"
                    }
                }
            },
            amount = new Amount
            {
                currency = "USD",
                total = "45.00",
                details = new Details
                {
                    tax = "5.00",
                    subtotal = "40.00"
                }
            }
        }
    },
    redirect_urls = new RedirectUrls
    {
        return_url = "http://www.somesite.com/order.aspx?return=true",
        cancel_url = "http://www.somesite.com/order.aspx?cancel=true"
    }
};

var createdPayment = payment.Create(apiContext); 

2. Create the payment.  
    

// Create the payment
var payment = new Payment
{
    intent = "sale",
    experience_profile_id = createdProfile.id,
    payer = new Payer
    {
        payment_method = "paypal"
    },
    transactions = new List<Transaction>
    {
        new Transaction
        {
            description = "Ticket information.",
            item_list = new ItemList
            {
                items = new List<Item>
                {
                    new Item
                    {
                        name = "Concert ticket",
                        currency = "USD",
                        price = "20.00",
                        quantity = "2",
                        sku = "ticket_sku"
                    }
                }
            },
            amount = new Amount
            {
                currency = "USD",
                total = "45.00",
                details = new Details
                {
                    tax = "5.00",
                    subtotal = "40.00"
                }
            }
        }
    },
    redirect_urls = new RedirectUrls
    {
        return_url = "http://www.somesite.com/order.aspx?return=true",
        cancel_url = "http://www.somesite.com/order.aspx?cancel=true"
    }
};

var createdPayment = payment.Create(apiContext); 

3. Redirect the buyer to PayPal using the approval_url HATEOAS link included with the created payment.
    

// Redirect buyer to PayPal to approve the payment...
var approvalUrl = createdPayment.GetApprovalUrl();

4. Once the buyer approves the payment and is redirected back to your site, execute the payment.
    

var payerId = Request.Params["PayerID"];
var paymentId = Request.Params["paymentId"];
var paymentToExecute = new Payment { id = paymentId };
var executedPayment = paymentToExecute.Execute(apiContext, new PaymentExecution { payer_id = payerId });