.Net Core 3.1 EF MySQL Database First

File > New Project > ASP.Net Web APP > [Set Project Name] >

Then Choose [.net core], [.net core 3.1], and [Web App]

this will create new project with the next default files

Include MySQL DB support

Tools > NuGet Package Manager > Package Manager Console

run the following commands in the Package Manager Console:
Install-Package Microsoft.EntityFrameworkCore.Tools

MySQL has two drivers, any of them should works perfect
Install-Package Devart.Data.MySql.EFCore

OR

Install-Package Pomelo.EntityFrameworkCore.MySql

Creating a Model Classes From MySQL Database through a command

update appsettings.json to contains connection string:

"ConnectionStrings": {
    "MyDB": "User Id=root;Host=localhost;Database=ddl_frontend;"}

the file will be like this after update

Run the next command in Package Manager Console

Scaffold-DbContext  -Connection name=MyDB -Provider Pomelo.EntityFrameworkCore.MySql -OutputDir Model -Context "MyDbContext" -DataAnnotations -Force

the command will create DB context class and Entity(Tables) classes 

Notes:

Entity(Tables) classes are just simple classes, representing the data, stored in the database.

The DB context class represents a session with the database and allows you to query and save instances of the entity classes.

Sample Entity Framework Code

Razor Pages

each razor page consists of frontend and backend code
and any new razor project contains start page "index.cshtml" and it inherit page design from "Shared\_Layout.cshtml"

user can write CS script in frontend page using the next tags

@{

//C# code here

}

ViewData dictionary

by default, razor page define a dictionary variable with name ViewData to exchange data between frontend and backend and used also, to send data to  "Shared\_Layout.cshtml"
this ViewData concept replace ViewBag in older versions, that has performance issue. 

[ViewData] Attribute

Add [ViewData] attribute before any public variable allow access it through ViewData dictionary in frontend.

Note that any Model public variable  can access also in frontend via the @Model.property

OnGet() , and OnPost()

Razor page by default handle two events (Get , and Post), but we can define more events using asp-page-handler



asp-page-handler="Delete" ==> OnPostDelete()
asp-page-handler="Edit" ==> OnPostEdit()
asp-page-handler="View" ==> OnPostView()

Redirect to another page 

Redirect to another page with querystring parameters

Razor Session variable

HttpContext.Session.SetString("Test String", "1");

var x= HttpContext.Session.GetString("Test String");