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ASP.NET Core []⚓︎

Resources

  • To be completed

architecture

stack

Creating the project with the dotnet cli⚓︎

Obviously you're going to need the latest .NET SDK (check it with dotnet check).

Standard new templates⚓︎

dotnet new mvc --name MyMvcWebApplicationProjectName
dotnet new sln --name MyMvcWebApplicationSolutionName
dotnet sln ./MyMvcWebApplicationSolutionName.sln add ./MyMvcWebApplicationProjectName.csproj

!!! Info: Using an OrchardCore Project

The following example is to create a new project with an OrchardCoreCMS template in the current directory:

```powershell
dotnet new install OrchardCore.ProjectTemplates # Optional: to install 'dotnet new' templates
dotnet new occms --name OrchardCoreTest
dotnet new sln --name OrchardCoreTest
dotnet sln ./OrchardCoreTest.sln add ./OrchardCoreTest.csproj
dotnet build --verbosity normal # Optional: testing that the project is building
dotnet run # Run Kestrel
```

Using Entity Framework Core⚓︎

📖 Following the Entity Framework Core for Beginners series on the .NET YouTube channel!

Creating a database⚓︎

  • Install NuGet packages:
    • Microsoft.EntityFrameworkCore
    • Microsoft.EntityFrameworkCore.Design
    • Microsoft.EntityFrameworkCore.Tools
    • Microsoft.EntityFrameworkCore.SqlServer (if you're planning to use SqlServer)
  • In VSCode, use 
    dotnet tool install --global dotnet-ef
  • Create the classes in /Models mirroring the data models
  • Create the database context in /Data/DATABASENAMEContext.cs
    • The connection string should not be hardcoded: instead it should be securely stored, e.g. follow here
    • If you don't want/need to create it manually, you could scaffold it together with the corresponding Controller

One way to do this is by storing them in a separate JSON file using User Secrets ([YourProject]>[Manage User Secrets]) that you can exclude from source control.

User secrets are automatically added to the appsettings.json configuration file, so they're available in the builder.Configuration object.

The snippet to be used when configuring the db context in Program.cs is 

builder.Services.AddDbContext<assistenza_backupContext>(options =>
    options.UseSqlServer(builder.Configuration.GetConnectionString("PARAMETERNAME")));
Where the parameter will appear in your secrets.json as: 
{
    "ConnectionString:PARAMETERNAME": "Data Source=(localdb)\\SQLEXPRESS; ..."
}
in VSCode, use dotnet user-secrets init then dotnet user-secrets set "PROPERTY" "VALUE"

⚠ secrets.json is not encrypted!

If you don't wish to use the User Secrets, you can add the connection string in the configuration file, for example: 

  "ConnectionStrings": {
    "DBNAME": "Server=SERVERNAME\\INSTANCENAME;Database=DBNAME;Trusted_Connection=True;"
  }

  • Create the database with the first initial create migration
    • In VS, use the Package Manager Console and type Add-migration InitialCreate
    • In VSCode, dotnet ef migrations add InitialCreate
  • Review the migration before committing it!
  • Apply the migration using:
    • In VS, the command Update-database in the Package Manager Console
    • In VSCode, dotnet ef database update

Using an existing database⚓︎

⭐ Start with this tutorial.

  • From the Package Manager Console, use Scaffold-DbContext "CONNECTIONSTRING" Microsoft.EntityFrameworkCore.SqlServer -ContextDir data -OutputDir Models -DataAnnotation where:
    • "CONNECTIONSTRING" is just the connection string, like "Server=(local)\localdb;Database=DB_NAME;Trusted_Connection=True"
    • Microsoft.EntityFrameworkCore.SqlServer is the provider
    • -ContextDir specifies the destination of the DbContext class
    • -OutputDir specifies the destination of the created Models
    • -DataAnnotation specifies the usage of Data Annotation
  • In VSCode, use dotnet ef dbcontext scaffold ... followed by the same options

  • Then, to match the scaffolded schema within the migration logic,

    • Add-migration InitialCreate to create the migration first script
    • Manually remove the content of the Up method in the script
    • Update-database to apply the migration

  • The fields in a model can be renamed by just changing the properties names (it will rename the corresponding db columns) and then migrating up

Applying migrations⚓︎

  • ❌ When applying the migration (upgrade-database...) if you ever encounter the error Execution Timeout Expired. The timeout period elapsed prior to completion of the operation or the server is not responding. Could not create constraint or index. See previous errors. Operation cancelled by user. The statement has been terminated. you may extend the command timeout using something like: 
    builder.Services.AddDbContext<YOUR_DB_CONTEXT>(options =>
    options.UseSqlServer(builder.Configuration.GetConnectionString("YOUR_DB_CONTEXT_CONNECTION_STRING"),
    opts => opts.CommandTimeout((int)TimeSpan.FromMinutes(5).TotalSeconds)));

Connect to multiple DBs⚓︎

Note: https://khalidabuhakmeh.com/how-to-add-a-view-to-an-entity-framework-core-dbcontext

First try connecting to multiple providers (e.g. MS Access & SQL Server )⚓︎

Following for instance this DEV article.

Migrate from MS Access to SQL Server⚓︎

  • Unfortunately, the MS Access JET provider for Entity Framework Core is not supported from EFCore>=6.0.0 and compatibility would require a downgrade to <5.0.0
  • Therefore, the best way is to convert your MS Access database into a more recent and supported RDBMS, e.g. SQL Server
    • Download and open SQL Server Management Assistant (SSMA) for Access
    • Convert all the objects in your MS Access database into object of a newly created empty SQL Server database
    • Add the new ODBC link to the new SQL Server database
    • In your UI/mask/report structure, update any linked table or query to the new data source
    • 🎭 There you go!

Finally, connecting multiple times to the same provider⚓︎

Following for instance this CodeMaze article.

  • Follow the instructions at the paragraph above for an existing database to scaffold the DbContext and the Models
  • Add the new connection string wherever your database connection configuration is stored

For instance, if you're using the user secrets or a separate json file, it may look like:

json { "ConnectionStrings": { "FIRST_DBCONTEXT_NAME": "FIRST_DBCONTEXT_CONNECTION_STRING", "SECOND_DBCONTEXT_NAME": "SECOND_DBCONTEXT_CONNECTION_STRING" } }

  • Add the new context in Program.cs with something like: 
    builder.Services.AddDbContext<YOURNEWCONTEXTNAME>(options =>
    options.UseSqlServer(builder.Configuration.GetConnectionString("CONNECTIONSTRINGNAME")));
  • Add the first migration by specifying the context, with Add-Migration MIGRATIONNAME -Context CONTEXTNAME
  • Remove the content of the Up method in the first migration file
  • Apply the first migration by using Update-database -Context CONTEXTNAME

Scaffold Razor Pages⚓︎

(i.e. automatically create CRUD pages)

  • Install Microsoft.VisualStudio.Web.CodeGeneration.Design

  • For each object you wish to scaffold the Razor Pages for:

    • In the Pages folder, add a new subfolder in your project, naming it like the object you want to scaffold (es. Interventions)
    • Right-click on the new subfolder and Add a scaffolded item
    • Select the Razor Pages with Entity Framework (CRUD) option
    • Select the specified class you wish to scaffold
    • Select the Database Context
    • The scaffolding process creates new files for each object to handle the Index, Create, Edit, Delete an Details features, both in:
      • .cshtml the actual C#-HTML page rendered
      • .cshtml.cs the code behind

  • In VSCode:

    • dotnet add package Microsoft.VisualStudio.Web.CodeGeneration.Design,
    • then dotnet tool install --global dotnet-aspnet-codegenerator
    • then dotnet aspnet-codegenerator razorpage --model MODELNAME --dataContext DBCONTEXTNAME --relativeFolderPath Pages/MODELNAMEs --referenceScriptLibraries

  • Test the model directly on the web app by running the debugger on IISExpress and going to http://localhost:PORT/MODELNAMEs

Controllers⚓︎

  • Controllers are routed using the app.MapControllerRoute method of the WebApplication instance

    • Multiple patterns can be used, the default one is "{controller=Home}/{action=Index}/{id?}
      • Meaning that the default route (/) is made by the Home controller (HomeController) on the default action Index with an optional id

  • The default HTTP method on Controllers is get (therefore, it's like every controller has the [HttpGet] attribute in front of it, except when specified otherwise)

    • For any POST method (like Create or Edit), both [HttpGet] and [HttpPost] methods are implemented, depending on the web request received
      • That's why there are two Edit methods (the first one shows the selected item's properties in the form, the second one updates the item with the edited values), but only one Create method

A little bit of style⚓︎

  • To play a bit with Bootstrap, you can use the free Bootswatch themes.
    • Example of CDN link for the Minty theme: https://www.bootstrapcdn.com/bootswatch/
    • jQuery required: https://cdn.jsdelivr.net/npm/jquery@3.6.0/dist/jquery.min.js

Building the solution⚓︎

  • ❌ If you ever encounter the error System.InvalidOperationException : No method 'public static IHostBuilder CreateHostBuilder(string[] args)' or 'public static IWebHostBuilder CreateWebHostBuilder(string[] args)' found on 'AutoGeneratedProgram'. Alternatively, WebApplicationFactory'1 can be extended and 'CreateHostBuilder' or 'CreateWebHostBuilder' can be overridden to provide your own instance., it looks like a Visual Studio bug. Just open your Program.cs file and launch build from there.