Replacing WCF with AspNetCore Rest API as transport layer for XPO

Replacing WCF with AspNetCore Rest API as transport layer for XPO

by | Sep 12, 2019 | DevExpress, netcore, Nuget, XAF, Xamarin, XPO

I have been using XPO from DevExpress since day one. For me is the best O.R.M in the dot net world, so when I got the news that XPO was going to be free of charge I was really happy because that means I can use it in every project without adding cost for my customers.

Nowadays all my customer needs some type of mobile development, so I have decided to master the combination of XPO and Xamarin

Now there is a problem when using XPO and Xamarin and that is the network topology, database connections are no designed for WAN networks.

Let’s take MS SQL server as an example, here are the supported communication protocols

  • TCP/IP.
  • Named Pipes

To quote what Microsoft web site said about using the protocols above in a WAN network

https://docs.microsoft.com/en-us/sql/tools/configuration-manager/choosing-a-network-protocol?view=sql-server-2014

Named Pipes vs. TCP/IP Sockets

In a fast-local area network (LAN) environment, Transmission Control Protocol/Internet Protocol (TCP/IP) Sockets and Named Pipes clients are comparable with regard to performance. However, the performance difference between the TCP/IP Sockets and Named Pipes clients becomes apparent with slower networks, such as across wide area networks (WANs) or dial-up networks. This is because of the different ways the interprocess communication (IPC) mechanisms communicate between peers.”

So, what other options do we have? Well if you are using the full DotNet framework you can use WCF.

So, it looks like WCF is the solution here since is mature and robust communication framework but there is a problem, the implementation of WCF for mono touch (Xamarin iOS) and mono droid (Xamarin Android)

You can read about Xamarin limitations in the following links

Android: https://docs.microsoft.com/en-us/xamarin/android/internals/limitations

iOS: https://docs.microsoft.com/en-us/xamarin/ios/internals/limitations

I don’t want to go into details about how the limitation of each platform affects XPO and WCF but basically the main limitation is the ability to use reflection and emit new code which is needed to generate the WCF client, also in WCF there are problems in the serialization behaviors.

Well now that we know the problem is time to talk about the solution. As you know XPO has a layered architecture ( you can read about that here https://www.jocheojeda.com/2018/10/01/xpo-post-5-layered-architecture/)

So basically, what we need to do is to replace the WCF layer with some other technology to communicate to the database server

The technology I’ve selected for this AspNetCore which I would say is a really nice technology that is modern, multi-platform and easy to use. Here below you can see what is the architecture of the solution

AspNetCore

Rest API

So, what we need basically is to be able to communicate the data layer with the data store through a network architecture.

The network architecture that I have chosen is a rest API which is one of the strong fronts of AspNetCore. The rest API will work as the server that forward the communication from XPO to the Database and vice versa, you can find a project template of the server implementation here https://www.jocheojeda.com/download/560/ this implementation references one nuget where I have written the communication code, you can fine the nuget here https://nuget.bitframeworks.com/feeds/main/BIT.Xpo.AgnosticDataStore.Server/19.1.5.1

Also we need a client that is able to interpret the information from the rest API and feed XPO, for that I have created a special client you can find here https://nuget.bitframeworks.com/feeds/main/BIT.Xpo.AgnosticDataStore.Client/19.1.5.1

The client implementation has been tested in the following platforms

  • Xamarin Android
  • Xamarin iOS
  • Xamarin WPF
  • DotNetCore
  • DotNetFramework

The client implementation has been tested in the following operative systems

  • Android 5 to 9
  • iOS 9 to 11
  • MacOS: Sierra to Catalina
  • Windows 10

In this link, you can see a full implementation of the server and the clients (XAF and Xamarin)

What is next? Well here are a few topics for the upcoming posts

  • Understanding JWT tokens
  • How to secure your data store service with a JWT token
  • Hosting multiple data store with a single service
  • Implementing your own authentication method
  • Examples examples examples

 

Xamarin Forms UWP / UAP Broad File System Access (Permissions)

by | Jan 26, 2019 | Forms, UAP/UWP, Xamarin

For a long time now, I have wanted to access the file system when I create a Xamarin Forms UAP/UWP application but that was actually impossible … till now. After the Windows 10 build 17134 update its possible to access the broad file system, the approach is not straight forward.

To gain access to the file system in your Xamarin Forms UAP/UWP application follow these steps

1) Go the properties of your UAP/UWP application and check the targeting, the minimum should be at least 16299, what I recommend is 171344

You can also change the targets unloading the project and editing the csproj file

2) In your solution explorer edit your Package.appxmanifest by selecting it and press F7, looking the file from the top should look like the image below

Add this namespace xmlns:rescap=”http://schemas.microsoft.com/appx/manifest/foundation/windows10/restrictedcapabilities and update the IgnorableNamesSpaces like this IgnorableNamespaces=”uap mp rescap” after the changes your file should look like the image below

3) Lookup for the capabilities node in the manifest and add a new capability  <rescap:Capability Name=”broadFileSystemAccess” /> your capabilities section should look like the image below

4) Rebuild your application, then select it on the solution explorer, right click over it and click on deploy, this will register the application in your OS

5) on your Windows OS go to settings>File system privacy settings and you will see all the UAP/UWP applications that are registered  in your OS and have access to the file system, here you can allow/deny the access to the file system in general or by application

6) now everything is ready for your app to access the file system, but there is a little catch, in most cases, you cannot use the classes in system.io to access the file system you have to use Windows.Storage.Storagefolder below is a code snippet that illustrates how to use such class

public async void GetDirectories(string sDir)
{
    
    var folder = await StorageFolder.GetFolderFromPathAsync(sDir);   
    foreach (var file in await folder.GetFilesAsync())
    {
        Debug.WriteLine(file.Name);
        
    }

}

 

I have created a sample app using these steps, you can download the source from GitHub