.net8 winform程序使用EntityFrameworkCore连接数据库

在.NET 8 WinForms应用程序中使用Entity Framework (EF) Core，你需要按照以下步骤操作：
1.添加Entity Framework Core NuGet包。
2.定义你的数据模型。
3.创建数据库上下文 (DbContext)。
4.在数据库上下文中配置Entity Framework。
5.使用Entity Framework Core的API来执行数据库操作。
以下是一个简单的示例：

安装Entity Framework Core NuGet包：
连接sqlserver数据库
dotnet add package Microsoft.EntityFrameworkCore
dotnet add package Microsoft.EntityFrameworkCore.SqlServer
dotnet add package Microsoft.EntityFrameworkCore.Tools

连接Mysql数据库
dotnet add package Microsoft.EntityFrameworkCore
dotnet add package Pomelo.EntityFrameworkCore.MySql
dotnet add package Microsoft.EntityFrameworkCore.Tools

定义数据模型：

using System.ComponentModel.DataAnnotations.Schema;
using System.ComponentModel.DataAnnotations;

namespace WinFormsApp.Models
{
    [Table("student")]
    public class Student
    {
        /// <summary>
        /// 主键，自增
        /// </summary>
        [Key, Column("id"), DatabaseGenerated(DatabaseGeneratedOption.Identity)]
        public int Id { get; set; }
        [Column("last_name"), StringLength(50)]
        public string LastName { get; set; } = string.Empty;
        [Column("first_mid_name"),StringLength(50)]
        public string FirstMidName { get; set; } = string.Empty;
        [Column("enrollment_date")]
        public DateTime EnrollmentDate { get; set; }
    }
}

创建数据库上下文：

using System.Configuration;
using Microsoft.EntityFrameworkCore;
using WinFormsApp.Models;

namespace WinFormsApp
{
    public class XCGDbContext : DbContext
    {
        public static readonly string ConnStr = ConfigurationManager.ConnectionStrings["MysqlContext"] + "";
        public static ServerVersion? SerVersion = null;
        public ServerVersion GetServerVersion()
        {
            if (SerVersion == null)
            {
                SerVersion = ServerVersion.AutoDetect(ConnStr);
            }
            return SerVersion;
        }
        #region DbSet
        public DbSet<Student> Students { get; set; }
        #endregion
        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {
            //连接mysql，需要安装 Pomelo.EntityFrameworkCore.MySql
            //string connStr = ConfigurationManager.ConnectionStrings["MysqlContext"] + "";
            //var serVersion = ServerVersion.AutoDetect(ConnStr);
            //optionsBuilder.UseMySql(connStr, serverVersion);
            
            //上面的方式在频繁操作数据库的时候报错
            optionsBuilder.UseMySql(ConnStr, GetServerVersion());

            //连接sql，需要安装 Microsoft.EntityFrameworkCore.SqlServer
            //optionsBuilder.UseSqlServer(@"Server=(localdb)\mssqllocaldb;Database=Blogging;Integrated Security=True");
        }
    }
}

在winform程序中使用EF Core：

using (var context = new XCGDbContext())
{
    // 添加
    context.Students.Add(new Student { EnrollmentDate = DateTime.Now, FirstMidName = "jay" + DateTime.Now.Ticks, LastName = "x" });
    context.SaveChanges();

    // 查询
    var stus = context.Students.ToList();

    // 更新
    foreach (var stu in stus)
    {
        stu.LastName = "star";
    }
    context.SaveChanges();

    // 删除
    var stuToDelete = context.Students.FirstOrDefault();
    context.Students.Remove(stuToDelete);
    context.SaveChanges();
}

使用以下命令来创建和应用数据库迁移：
dotnet ef migrations add InitialCreate
dotnet ef database update

添加一个配置文件app.config

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
    <appSettings>
        <add key="Setting1" value="Value1" />
    </appSettings>
    <connectionStrings>
        <add name="MysqlContext" connectionString="server=localhost;port=3306;database=xcgdb;uid=root;pwd=root;charset=utf8mb4;"/>
    </connectionStrings>
</configuration>