Apple Pay with a .NET Backend

I saw a question and submitted my solution here https://developer.apple.com/forums/thread/653672?answerId=681767022#681767022. I’ll copy/paste here in case it’s easier to find.

Requesting an Apple Pay Session in .NET

I was able to get this working! The thing that's most important to know is that you CANNOT just import the .cer file from your developer portal into your Windows cert store and start attaching it to your requests. In order to get it to work, I had to:

1. Create a .pfx file (which will, by nature, contain both the cert and its key) as shown here: https://blog.aclerbois.be/blog/2020/01/09/Generates-a-pfx-for-Apple-Pay

2. Import the generated .pfx file into my Windows cert store.

3. Attach the cert to my WebRequestHandler

Here's my C# code:

public async Task GetSessionAsync(string validationUrl = null)

    {
        var sessionRequestBody = new ApplePaySessionRequest
        {
            merchantIdentifier = ConfigurationManager.AppSettings["ApplePayMerchantIdentifier"],
            displayName = "DISPLAY NAME",
            initiativeContext = ConfigurationManager.AppSettings["ApplePayInitiativeUrl"]
        };

        var handler = new WebRequestHandler();       
        handler.ClientCertificates.Add(GetCertificate(MerchantIdentityCertThumbprint));            

        var client = new HttpClient(handler);

        var url = !string.IsNullOrWhiteSpace(validationUrl) ? validationUrl : PaymentSessionEndpointUrl;
        var response = await client.PostAsJsonAsync(url, sessionRequestBody);
        var applePaySession = await response.Content.ReadAsAsync<ApplePaySession>();
        return applePaySession;
    }

    private X509Certificate2 GetCertificate(string certThumbprint)
    {
        X509Store userCaStore = new X509Store(StoreName.My, StoreLocation.CurrentUser);

        try
        {
            userCaStore.Open(OpenFlags.ReadOnly);
            X509Certificate2Collection certificatesInStore = userCaStore.Certificates;
            X509Certificate2Collection findResult = certificatesInStore.Find(X509FindType.FindByThumbprint, certThumbprint, false);
            X509Certificate2 clientCertificate = null;
            if (findResult.Count == 1)
            {
                clientCertificate = findResult[0];
            }
            else
            {
                throw new Exception("Unable to locate the correct client certificate.");
            }
            return clientCertificate;
        }
        catch
        {
            throw;
        }
        finally
        {
            userCaStore.Close();
        }
    }

Javascript Tip: Datez

A quick one!

A coworker of mine had an interesting problem regarding cross-browser javascript dates.  

Does this look fine to you?

new Date('2016-08-29T14:42:07.56')

It looks fine to me.  It turns our it's not fine. In order for this code to return you an expected datetime across browsers (in our case Chrome and IE), we should specify either a timezone or a specific offset.  Since we didn't particularly care to add a specific offset, we used

new Date('2016-08-29T14:42:07.56Z')

Yep, we just slapped a "Z" on there.  Apparently, "Z" is a zero-time UTC offset (-00:00).  

This happens because Chrome assumes an unspecified date to be a UTC time with a zero-offset, while IE assumes the timezone should be the same timezone of the client machine (in our case, EST, -05:00).

If you wanted to specify your particular locale's offset, you could construct the date this way

new Date('2016-08-29T14:42:07.56Z-05:00')

Thanks to Moshe Karmel for the advice!  

For reasons like this, I tend to use momentjs for basically everything having to do with dates.