asp-mysql

database first

use entity generate models

// toolset of entity framework
dotnet tool install --global dotnet-ef
dotnet tool update --global dotnet-ef

// install package
Pomelo.EntityFrameWorkCore.MySql
Microsoft.EntityFrameworkCore
Microsoft.EntityFrameworkCore.Design

// dotnet command reference https://docs.microsoft.com/en-us/ef/core/cli/dotnet
// change to project folder that contains .csproj file, not sln file's folder， output files will be present in models folder
dotnet ef dbcontext scaffold "Server=192.168.0.129;User=root;Password=lanbe123;Database=monitor" "Pomelo.EntityFrameworkCore.MySql" -o ./models

// 在生成的文件夹里面找到 monitorContext.cs 里面有生成的工具类

// Startup.cs
 public void ConfigureServices(IServiceCollection services)
{
    // Replace with your connection string.

    services.AddDbContext<monitorContext>(
        dbContextOptions => dbContextOptions
            .UseMySql(Configuration["ConnectionStrings:ConnMySql"], new MySqlServerVersion(new Version(5, 7, 19)))
            // The following three options help with debugging, but should
            // be changed or removed for production.
            .LogTo(Console.WriteLine, LogLevel.Information)
            .EnableSensitiveDataLogging()
            .EnableDetailedErrors()
    );

    services.AddControllers();
}

EF query

Entity framework supports three types of queries: 1) LINQ-to-Entities, 2) Entity SQL, and 3) Native SQL

Entity SQL

Entity SQL is another way to create a query. It is processed by the Entity Framework’s Object Services directly. It returns ObjectQuery instead of IQueryable.
You need an ObjectContext to create a query using Entity SQL.
The following code snippet shows the same query result as the LINQ query above.

//Querying with Object Services and Entity SQL
string sqlString = "SELECT VALUE st FROM SchoolDBEntities.Students " +
                    "AS st WHERE st.StudentName == 'Bill'";
    
var objctx = (ctx as IObjectContextAdapter).ObjectContext;
                
ObjectQuery<Student> student = objctx.CreateQuery<Student>(sqlString);
Student newStudent = student.First<Student>();

Native SQL

using (var ctx = new SchoolDBEntities())
{
    var studentName = ctx.Students.SqlQuery("Select studentid, studentname, standardId from Student where studentname='Bill'").FirstOrDefault<Student>();
}    

delete

var us = db.user.FirstOrDefault(x => x.uid == uid);

db.user.Attach(us); 
db.user.Remove(us);