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Project Development Walkthrough

Preface

This is merely to get an idea of how to go about thinking with projects. Many steps are skipped or ignored for the sake of simplicity (eg many minor things in ticket for whats being imported aren’t important for the general idea).

1. Take a look at the ticket

https://jira.hutility.com/projects/P658/issues/P658-1

2. Clone the repo

Find the git url from https://code.hutility.com:3000/Hutility/658 (can find it through mapper https://code.hutility.com:3000/mapper/repos/664 if needed) in this case it is https://code.hutility.com:3000/Hutility/658.git. Now clone the repo, the way I approach this is to have a network directory with all of my git repos so that I can access it from any VM. For naming I begin with the project number and some relevant name (658 CB Squared AR Import) this makes it easy to find it in the directory.

3. Create the project

Create a new project using the latest Hutility AccPac Template (in this case it is Hutility AccPac Template 2017 10 11). Set the location to be within your cloned repo in a Source folder. Initially it may look like there are errors, build the project so that NuGet packages are downloaded.

4. Plan out the project structure

You can jot down ideas or go straight to putting together some of the below components if it is straight forward enough. The idea is to separate concerns so that each piece has an obvious single function. The more convoluted a class is, the more difficult it is to test, update or even read. Horizontal bloat is much better than vertical bloat (make more short classes instead of less large classes).

4.1 Models

Think about the requirements and identify the models you will need. Rather than pulling information and using it right away it is often preferable to populate the data, store it in a class (model) and then process it in another location. This way the processing/import functionality is separated from the populating functionality which often should not intertwine directly.
 
The reason this is preferable to combining the population and import functionality together is it is much easier to understand, test and debug. For example – if we have a Pull Invoices function that creates a list of Invoice Line classes and an Import Invoice function that accepts them. We can easily see after the Pull Invoices call if it pulled correct data. Likewise inside the Import Invoice command we can see the populated Invoice Line classes before the import and what happens after. Without the intermediate step of storing the data in model classes you would have a lot more difficulty tracing issues.
 
Back to our example. At first glance there is one obvious model we need. The query returns a list of invoice detail lines. We can store each line as its own model. I created a folder called Models and added a public class called InvoiceLine, the properties of which are the different columns that come out of the query.

4.2 Services

Now that we have the models, think about all the interactions we will need to do eg: importing, exporting, converting. Depending on what these actions are doing you may create one more more services. A service will be a collection of methods within a certain domain. The template starts with SageService, this is built into the template since the template is normally used with Sage interactions in mind and some other portions of the template need to know what connection we are using.
 
For this project it looks like we will also be querying another database/table. It would make sense for a service separate from Sage to handle this. To deal with these operations I added a new class to the Services folder called EntityService. I will use this to perform the query and return a list of InvoiceLines. For importing into Sage it is easy enough to add a new function to SageService that will take InvoiceLines and perform the import.

4.3 User Interface

For every project there must be at least some user interface component, even if it is as simple as a button. For more complicated projects you may have to create more views, in cases like this you may want to create more view model classes if it makes sense in the hierarchy. This can be a complicated topic so I will leave complicated implementations for another post.

4.4 How they fit together

So now we have a service that can create InvoiceLines and a service that can import them into Sage but we need to combine the two for the program to be useful. Usually this will be the ViewModel (the primary one or new ones you create) that ties them together.

5. Implementation

5.1 InvoiceLine

This class is very simple it is just one property per column created from the query. We do add one thing which will come into use later however. Add the Mappable attribute to the class. (it is from HuLib)

5.2 EntityService

The first thing to note is that we will need sql information for the import so we can add this as constructor arguments (it doesn’t make sense to do anything in this service without a connection). Following that we w ill need the function to get the invoice data.

public EntityService(string server, string database, string user, string pass)
public IEnumerable GetInvoiceData(DateTime dateFrom, DateTime dateTo)

Since a single connection would likely be used for the lifespan of the EntityService, the constructor just creates the connection using the parameters. To make it simpler another HuLib function is used:

_connection = SQLUtility.CreateConnection(_server, _user, _pass, _database);
To populate the invoice data we simply populate a list of invoice lines using another hulib function:
IEnumerable invoiceLines = _connection.FillClasses(query);
What this function does is for each property in the InvoiceLine class it will find a column with the same name and pull its value. It does this for each record pulled by the query to give you a list of populated objects. The Mappable attribute from 5.1 is used to indicate that all properties can be mapped this way (you can also use Mapping attribute on individual fields instead).
 
Great now we have an EntityService class that is able to pull the data we need.

5.3 Wiring up EntityService properties (Config and UI)

Now would be a good time to write tests for EntityService if we were going to do so. What I do at this point is wire up the UI components including the Import button to pull data from EntityService but not actually do the import. The reason for this is so I can verify that the pulling data portion works before writing the import logic. That way we can identify that at least part of the application is working and if there are any architecture changes that are needed for this half we can do them without having to rework the import logic.
 
This is the benefit of separating the pulling data and import logic, we can use each part on its own without effecting the other.
 
Now note that to use EntityService we needed the connection information. It would be nice if this could persist between executions of our application. This is where the Config class comes in handy. Properties added to this class will persist between executions (they are loaded on startup, saved when the application closes).
 
4 properties are added to Config: Server, Database, User, Password. The first 3 of these are simply strings. The 4th a type is used called EncryptedString, this is because we do not want to store the password in plaintext (a security no-no). EncryptedString is serializable, is encrypted in memory and can actually be implicitly casted into string (and used in place of a string as a string argument) this makes it very easy to use (in most cases you can use it as if it was a normal string).
public string Server { get; set; }
public string Database { get; set; }
public string User { get; set; }
public EncryptedString Password { get; set; }
Now we need to set these within the UI. These settings will likely be changed very infrequently, so storing them on the main window would be overkill. Luckily the newest template has another view we can use – the ConfigurationWindow.xaml window will be where we put these properties.
 
Looking at the ConfigurationWindow, find where there is a commented out password box and its associated label, this is an example of adding to the configuration section of this screen. For each property add a label and textbox pair, except for the password, which will use the BindablePasswordBox control.

  

 

 

 

Now that our configuration window is set up, lets allow it to be shown from the main window. Open up MainWindow.xaml and uncomment the line that shows it within the tools menu:
 
 
We should now be able to run the program, open Tools>Edit Configuration, change values, close the program, reopen it and the settings will still be there. (Note you must properly close the program, not terminate via Visual Studio)

5.4 Wiring up the button for EntityService

Now for the button. The button will need to be connected to a command, in this case it will likely  be a longer running command. To make it a better experience to the user it would be useful to have the application indicate it is processing. Luckily the template makes this much easier as well.
 
Lets start with the ViewModel.cs class. Create the import function:
public void Import()
{
   EntityService entityService = new EntityService(Config.Server, Config.Database, Config.User, Config.Password);
   IEnumerable invoiceLines = entityService.GetInvoiceData(DateFrom, DateTo);
}
Note that DateFrom and DateTo were added to the view model as public properties.
 
Declare a new command in ViewModel called ImportCommand.
public ICommand ImportCommand { get; }
 
The command does not yet do anything as we will set it up in the constructor. In this case we do not want to use a RelayCommand (which is used for a blocking operation that would freeze the UI). We should use an AsyncCommand, these require many parameters so to make it easier we can use an AsyncCommand factory. Within the constructor find the commented line
AsyncCommandFactory commandFactory = new AsyncCommandFactory(StateManager, "Loading....");

Uncomment this and use it to create the new asynchronous command:

AsyncCommandFactory commandFactory = new AsyncCommandFactory(StateManager, "Loading....");
ImportCommand = commandFactory.Create(Import);

Thats it for the view model! Now to wire it up to the MainWindow.xaml. Find within MainWindow.xaml the grid that has a comment indicating it is where to add view code. We want to add a date from and to as well as a button to perform the import:

5.5 Test the pulling of data

Great now everything should be wired up (except the Sage portion of course), lets give it a run. Run the application, edit the configuration with the correct sql information and hit import. Placing a breakpoint at the end of the Import function can help us see what came out of the function (hopefully the invoice detail rows). If an error occurs note that the program doesn’t crash – the async command handles these cases for us and politely shows a textbox regarding the issue.

5.6 Implementing Sage Import

At this point this becomes so project specific that I won’t bother going into too much detail on this case. But here is the general idea behind implementing Sage interactions:
1. Do it in the Sage UI, or at least something similar to it
2. Replicate what you did in the UI this time running Record Macro before
3. Stop Recording, and copy the macro over to the Macro Converter to get C# code (find latest at \\build1\Artifacts\400 Tools)
4. Copy over the C# to a new function in SageService
 
In our case we will create a new method
public void Import(IEnumerable lines)
 
Now we simply add this to the view model’s import function and display a text box that it was successful after!

5.7 Finishing touches

Head over to AppSettings.cs and take a look at the constants there. You should change things to what makes sense for your project (you will likely change the Project Repo # and the name).
Open the project’s properties. Change the Assmbly name.
Still inside project properties open up Assembly Information and change the Title and Product.
Done!

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