From concept to reality in 6 weeks - part 9.5

After an shockingly bad Thanksgiving break, I need to quickly recover and focus on the task at hand of getting the app done as I have exactly five weeks left before the deadline hits. Really I am at day 10 since I have day 8.5 and now today is day 9.5. Of course that is not 25 days like it would seem as I have Christmas and New Year's Day breaks in there to deal with. I do have the weekends if I have to catch up for lost time. So let's just pretend I have 25 days left. Let's quickly recap what is working I have done so far:

• Day 1 - working Windows 8 laptop
• Day 2 - development environment Windows 8.1 SDK working on laptop
• Day 3 - Bing Maps displaying
• Day 4 - retrieve data from remote server
• Day 5 - learn Metro UI & 3rd party component libraries
• Day 6 - use single bottom AppBar
• Day 6.5 - learn how to submit app to Windows Store
• Day 7 - custom icons & fonts + deliver 1st iteration to customer
• Day 8 - component framework lifecycle to learn about dialogs
• Day 9 - retrieve live data from secure server and process as JSON

So that brings us up to today as I need to finish the JSON parsing, but first I need to make sure I understand how to get the free 3rd party component library I downloaded to work in my app. Last week I downloaded the free license and was not able to get the Perpetuum demos to work. This morning I am going to start that process one more time. There are a couple of reasons why I need to get this working today. I have received daily messages from the developer working on our 3rd party mapping engine and I need to meet him this evening to try to get his stuff working on my machine. I really need to make sure I know how to do this with another 3rd party library first.

I went back to look at the two emails I received from Perpetuum Software which were in response to me not getting their demos to work. It was a free license which means I get no support, but I really thought it was in their best interest to at least help me a bit with their demos since they came with no documentation. The first thing I did was add the original demo project and license files on my SkyDrive from my Mac. Then I deleted the project I had on Windows and started over. I had to retarget the project to Windows 8.1. I then opened the "App.xaml.cs" file and added my free license on the correct line and uncommented out the line. I rebuilt the project and saw the same error but then it went on to build the project.

Error occurred while restoring NuGet packages: System.ArgumentException: The path is not of a legal form

I pretended to not see that error and then ran the project file and it worked. Now I am feeling like I am off to a good start for my half day today!

I then went back into my email to look at the 2nd message on how to get the Perpetuum components to work in my app. I was told to find the DLL folder in the PerpetuumSoft.Controls.Demo project and copy that into my app project, so I followed those directions. I then right clicked on References and clicked on "Add Reference..." and then opened the Browse section on the left and clicked on the "Browse..." button. I then navigated to the PerpetummDll folder I created and added the PerpetuumSoft.Controls.dll and PerpetuumSoft.WinRT.Framework.dll, which resulted in PerpetuumSoft.Controls and PerpetuumSoft.WinRT.Framework showing up on the References section. I then opened my App.xaml.cs file and on the first line in the App constructor, I started typing "perp" and VSE completed PerpetuumSoft and kept completing until I had the following:

PerpetuumSoft.WinRT.Framework.Licensing.LicenseManager.SetKey(@"");

I then added the contents of the email I received with my license key between the double quotes. I rebuilt my app and received no errors. I did not use any of the components but at least it is building. That is good enough for now but eventually I will use their calendar and dual range selectors, so I switch back to finishing off the JSON parsing...

A couple of new lessons to learn at the beginning before I start. First is how to create an abstract method that I implement in subclass? I need to declare the method as "public abstract Process(string text)" in the parent class and then in all subclasses I need to declare it as "public override Process(string text)". That makes sense - I just needed to re-learn how to do it. Next I have to learn how to compare two strings. I first tried string.Equals(string) but that was a failure to compile. I looked up the String class and found a static Compare method so I tried that but it failed in the very same way:

The best overloaded method match for "string.Compare(string, string)" has some invalid arguments

 That is an odd message since this is exactly how the documentation says it should work. Then I look at the second error associated with the same line, which is

Argument 2: cannot convert from 'method group' to 'string'

Then I remember that I forgot to add "()" when calling a method as it was trying to pass a method to the Compare function. That is going to get me every time until I remember it unfortunately. But the good news is that all of my changes compile. Now I need to implement one of the process methods to make sure the JSON I retrieve from the server will be stored correctly in my DAO objects I created on Day 9. That means I need to learn how to process and array of JSON objects as well as how to change the ToString method so I can see the results of my parsing. I also need to know how to work with C# Arrays. If I can going to do all that then I need to know how to concatenate strings to show arrays within my ToString method. That should take care of my learning for the day as I will put all of that into action for my JSON parsing and checking the results.

I definitely fixed one bug where I was calling "await" in the wrong place. I found this article which describes how to determine the state of the app in the main App.xaml.cs file. In that method I called:

MainPage.Current.WaitForDownloads();

Which is very simple and checks for out standings running tasks:

public async void WaitForDownloads() { await DiscoverActionDownloadsAsync(); }

The method being called is very similar to the code I found in the Background Transfer sample code, with the primary different being how to output is logged.

Unfortunately, now two of my remote server calls are returning JSON but when I process the first JSON response I am getting a "System.NullReferenceException", but I have no clue where that occurred since the VSE debugger stops in a place that does not help me at all as it is in an "await" block. I went to the DEBUG menu and look under the Windows sub-menu and selected "Call Stack" to see that helped me but it did not. I went back into the debugger and inspected DownloadOperation variable to see the RequestedUri and now I know which server request is the one that fails. It turns out that is the one I have not written yet but I double checked the code and I don't see what the problem is. I set a break point in the code where I parse the results and it did not get to there yet.

Time for tennis so this will have to wait until tomorrow.