In order to follow this section, you won't need the WinForms app from the first edition—any WinForms app will do; however, it is recommended that you use that application, especially for the later section where we will discuss C# 8 features.

You can download the original project from the following location:

https://github.com/PacktPublishing/CSharp7-and-.NET-Core-2.0-Blueprints

If you download and run the application, you should see that it still works fine:

Let's now investigate how we can run this exact same code base under .NET Core 3. We'll start with the project file. Basically, we need to tell Visual Studio that we now have a .NET Core 3 project, and not a Framework one.

If you have PowerTools installed (https://marketplace.visualstudio.com/items?itemName=VisualStudioProductTeam.ProductivityPowerPack2017), you can do this from within Visual Studio; if not, then simply open the .csproj file using your favorite text editor:

Change the contents of the .csproj file to the following:

<Project Sdk="Microsoft.NET.Sdk.WindowsDesktop">
 
  <PropertyGroup>
    <OutputType>WinExe</OutputType>
    <TargetFramework>netcoreapp3.0</TargetFramework>
    <LangVersion>8.0</LangVersion>
    
    <AssetTargetFallback>uap10.0.18362</AssetTargetFallback>
    <UseWindowsForms>true</UseWindowsForms>
  </PropertyGroup>
 
  <ItemGroup>
    <PackageReference Include="Newtonsoft.Json" Version="12.0.2" />
  </ItemGroup>
 
  <ItemGroup>
    <ProjectReference Include="..\eBookManager.Controls\eBookManager.Controls.csproj" />
    <ProjectReference Include="..\eBookManager.Engine\eBookManager.Engine.csproj" />
    <ProjectReference Include="..\eBookManager.Helper\eBookManager.Helper.csproj" />
  </ItemGroup>
 
  <ItemGroup>
    <Reference Include="System">
      <HintPath>System</HintPath>
    </Reference>
  </ItemGroup>
  
</Project>    

This is, essentially, all that's needed; however, you will need to decide what to do about the project's resources. You can manually just check that they are all set to copy to the output directory; alternatively, we can add an ItemGroup to the project file, such as the following:

  <ItemGroup>
    <None Update="ico\importBooks.ico">
      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
    </None>
    <None Update="ico\mainForm.ico">
      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
    </None>
    <None Update="img\add_ebook_to_storage_space.png">
      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
    </None>
    <None Update="img\add_new_storage_space.png">
      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
    </None>
    <None Update="img\docx16.png">
      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
    </None>
    <None Update="img\docxx16.png">
      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
    </None>
    <None Update="img\eBook.png">
      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
    </None>
    <None Update="img\epubx16.png">
      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
    </None>
    <None Update="img\folder-close-x16.png">
      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
    </None>
    <None Update="img\folder_exp_x16.png">
      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
    </None>
    <None Update="img\image sources.txt">
      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
    </None>
    <None Update="img\no_eBook.png">
      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
    </None>
    <None Update="img\pdfx16.png">
      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
    </None>
    <None Update="img\ReadEbook.png">
      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
    </None>
    <None Update="img\storage_space_cloud.png">
      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
    </None>
  </ItemGroup>

As you can see, the whole thing is a great deal simpler than the previous version of the file.

The next step is to delete the following files, found under Properties:

• AssemblyInfo.cs
• Settings.Designer.cs
• Settings.settings

In fact, by the end of this chapter, the entire Properties folder will be gone.

Actually, that's it. Simply reload the project and hit F5. The app is now running under .NET Core. However, it's very likely you'll get an error at this point. The reason is that we have two other projects that are still running under .NET Framework:

• eBookManager.Engine
• eBookManager.Helper

We'll need to migrate each project in a similar way; let's start with eBookManager.Engine. As before, edit the project file and replace what you find there with the following:

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <TargetFramework>netcoreapp3.0</TargetFramework>
  </PropertyGroup> 
</Project>

As you can see, this is even simpler than before. In fact, it is not necessary to have this target 3.0; we could target 2.2, or even 2.1 if we so chose. Again, we'll delete AssemblyInfo.cs.

Finally, we come to eBookManager.Helper. Edit the project file again to match the following:

<Project Sdk="Microsoft.NET.Sdk"> 
  <PropertyGroup>
    <TargetFramework>netcoreapp3.0</TargetFramework>
  </PropertyGroup>
 
  <ItemGroup>
    <PackageReference Include="Newtonsoft.Json" Version="11.0.2" />
  </ItemGroup>
 
  <ItemGroup>
    <ProjectReference Include="..\eBookManager.Engine\eBookManager.Engine.csproj" />
  </ItemGroup>
</Project>

Again, we'll delete AssemblyInfo.cs. We'll also need to remove a stray reference to System.Windows.Forms in ExtensionMethods.cs.

Finally, we'll need to restructure some of the code that depends on embedded image resources. If you run the code as-is, you'll likely get an error similar to the following:

At the time of writing, WinForms on .NET Core 3.0 doesn't support binary serialization. As a result, we need to make a few small changes.

The first thing we'll need to do is to read the files from the output directory, so we'll change the Copy to Output Directory setting on the image and icon files; highlight all the files, and then change the Copy to Output Directory action to Copy if newer:

The next step is to go to the eBookManager screen.

In the eBookManager.Designer.cs file, remove the imageList1 section:

Also remove the btnReadEbook section:

And finally, remove the this.Icon assignment in the eBookManager section:

We'll move the code that has been removed into the Form_Load event of eBookManager.cs:

private void Form1_Load(object sender, EventArgs e)
{
    System.ComponentModel.ComponentResourceManager resources = new System.ComponentModel.ComponentResourceManager(typeof(eBookManager));
 
    this.components = new System.ComponentModel.Container();
 
    // imageList1
    //this.imageList1.ImageStream = ((System.Windows.Forms.ImageListStreamer)(resources.GetObject("imageList1.ImageStream")));            
    this.imageList1.Images.Add("storage_space_cloud.png", Image.FromFile("img/storage_space_cloud.png"));
    this.imageList1.Images.Add("eBook.png", Image.FromFile("img/eBook.png"));
    this.imageList1.Images.Add("no_eBook.png", Image.FromFile("img/no_eBook.png"));
    this.imageList1.TransparentColor = System.Drawing.Color.Transparent;
 
    // btnReadEbook            
    this.btnReadEbook.Image = Image.FromFile("img/ReadEbook.png");
    this.btnReadEbook.Location = new System.Drawing.Point(103, 227);
    this.btnReadEbook.Name = "btnReadEbook";
    this.btnReadEbook.Size = new System.Drawing.Size(36, 40);
    this.btnReadEbook.TabIndex = 32;
    this.toolTip1.SetToolTip(this.btnReadEbook, "Click here to open the eBook file location");
    this.btnReadEbook.UseVisualStyleBackColor = true;
    this.btnReadEbook.Click += new System.EventHandler(this.btnReadEbook_Click);
 
    // eBookManager Icon            
    this.Icon = new System.Drawing.Icon("ico/mainForm.ico");
 
    PopulateStorageSpaceList();
}

A similar change is needed for importBooks.Designer.cs. The following section should be removed:

Remove the setter for the btnAddeBookToStorageSpace image in the same file:

Remove the image for btnAddNewStorageSpace (again, in the same file):

Finally, remove the icon setter for the form:

We'll move this into the Form_Load event of ImportBooks.cs, which should now look as follows:

private void ImportBooks_Load(object sender, EventArgs e)
{
    // tvImages                        
    this.tvImages.Images.Add("docx16.png", Image.FromFile("img/docx16.png"));
    this.tvImages.Images.Add("docxx16.png", Image.FromFile("img/docxx16.png"));
    this.tvImages.Images.Add("pdfx16.png", Image.FromFile("img/pdfx16.png"));
    this.tvImages.Images.Add("epubx16.png", Image.FromFile("img/epubx16.png"));
    this.tvImages.Images.Add("folder-close-x16.png", Image.FromFile("img/folder-close-x16.png"));
    this.tvImages.Images.Add("folder_exp_x16.png", Image.FromFile("img/folder_exp_x16.png"));
    this.tvImages.TransparentColor = System.Drawing.Color.Transparent;
 
    // btnAddeBookToStorageSpace
    this.btnAddeBookToStorageSpace.Image = Image.FromFile("img/add_ebook_to_storage_space.png");
    
    // btnAddNewStorageSpace
    this.btnAddNewStorageSpace.Image = Image.FromFile("img/add_new_storage_space.png");
 
    // ImportBooks            
    this.Icon = new System.Drawing.Icon("ico/importBooks.ico");
 
 
    PopulateStorageSpacesList();
                
    if (dlVirtualStorageSpaces.Items.Count == 0)
    {
        dlVirtualStorageSpaces.Items.Add("<create new storage space>");
    }
 
    lblEbookCount.Text = "";
}

Finally, the following will need to be changed in eBookManager.cs:

private void btnReadEbook_Click(object sender, EventArgs e)
        {
            string filePath = txtFilePath.Text;
            FileInfo fi = new FileInfo(filePath);
            if (fi.Exists)
            {
                var processStartInfo = new ProcessStartInfo(filePath, Path.GetDirectoryName(filePath))
                {
                    // Change in .NET Core - this defaulted to true in WinForms
                    UseShellExecute = true
                };
                Process.Start(processStartInfo);
            }
        }

The reason is that ProcessStartInfo in .NET Framework used to default to UseShellExecute = true. However, in .NET Core, it now defaults to false, and will therefore fail without this change.

That's it! If you run the app, you're now running it under .NET Core 3. It's the same application (albeit with some minor code changes), but now it's running the .NET Core runtime!

Let's start with the elephant in the room. You can't now take Ebook Manager and run it on Linux—it is not now cross-platform. WinForms always was, still is, and probably always will be, a Windows-specific technology.

Upgrading essentially gives you three benefits:

• Speed: .NET Core 2.1 saw some significant speed improvements. Your mileage may vary with this, and it's likely that it will depend on exactly what your application is doing. For example, the Ebook Manager application scans the hard drive to retrieve books: it's unlikely that the memory allocation improvements made in .NET Core 2.1 are going to make a huge difference to the speed of that.

• Support: Once you've upgraded to .NET Core, your app will now be running on a far more active piece of technology; in the future, Microsoft is less likely to change .NET Framework, except for security bug patches, but .NET Core has an active road-map.

• Enthusiasm: It's hard to get people excited about (or to get people at all) working on a WinForms application written fifteen years ago.

C# 8 brings a host of new features to the table, including the following:

• Nullable reference types
• Default implementations of interfaces
• Records
• Recursive patterns
• Async streams
• Ranges
• Static local functions
• Using declarations

Taking the top two headline features from that list, it's clear that there is synergy between being able to run legacy code in .NET Core 3 and being able to apply some of these features to help to update and maintain legacy code.