public class EFCoreDbContext:DbContext
    {
        private string strConn = "Server=.;Database=EFCoreDB01;Trusted_Connection=True";

        
        public EFCoreDbContext(string strConn)
        {
            this.strConn = strConn;
            //strConns.ad
        }

       
        

        /// <summary>
 

        /// 每一個表對應資料庫對映
        /// </summary>
        public DbSet<UserInfo> UserInfo { get; set; }


        /// <summary>
        /// 配置資料庫連線
        /// </summary>
        /// <param name="optionsBuilder"></param>
        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {
            
 
//Nuget引入：Microsoft.EntityFrameworkCore.SqlServer
            optionsBuilder.UseSqlServer(strConn);//資料庫連線
        }


        /// <summary>
        /// 配置資料庫結構，關係對映
        /// </summary>
        /// <param name="modelBuilder"></param>
        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            
 
//初始化資料庫
            modelBuilder.Entity<UserInfo>().HasData(new List<UserInfo>()
            {
                new UserInfo()
                {
                    UserId=1,
                    UserName="張三",
                    Description="好學生",
                    UserAge=33
                },
                new UserInfo()
                {
                    UserId=2,
                    UserName="李三",
                    Description="不太好學生",
                    UserAge=31
                },
                new UserInfo()
                {
                    UserId=3,
                    UserName="王五",
                    Description="學生",
                    UserAge=34
                }
            });
        }


    }

生成資料庫
1,通過Api生成(下面方法)
2，工具生成
3，遷移檔案生成

EFCoreDbContext context = new EFCoreDbContext();
                context.Database.EnsureDeleted();//判斷如果有資料庫，就刪除資料庫
                context.Database.EnsureCreated();//建立一個新的資料庫

單Context多資料庫連線管理

public class EFCoreContextFactory
    {
        private const string writeConnection = "Server=.;Database=EFCoreDB01;Trusted_Connection=True";
        public static List<string> strConns = new List<string>()
        {
            "Server=.;Database=EFCoreDB01_Read01;Trusted_Connection=True",
            "Server=.;Database=EFCoreDB01_Read02;Trusted_Connection=True"
        };

        private static EFCoreDbContext context=null;

        public static EFCoreDbContext createDbContext(WriteOrRead writeOrRead)
        {
            switch (writeOrRead)
            {
                case WriteOrRead.Write:
                    context = new EFCoreDbContext(writeConnection);
                    break;
                    //主庫連線 
                case WriteOrRead.Read:
                    context= new EFCoreDbContext(GetReadConnect());
                    //從庫連線
                    break;
                default:
                    break;
            }
            return context;

        }

        //1,當前請求數量
        private static int _currentRequestCount = 0;
        private static string GetReadConnect()
        {
            //定義一個輪詢策略
            //根據請求量來取模
            int currentIndex = _currentRequestCount % strConns.Count;
            _currentRequestCount++;
            return strConns[currentIndex];

            //定義一個隨機策略
           // int i = new Random().Next(0, strConns.Count);
           // return strConns[i];

        }


    }

 

    public enum WriteOrRead
    {
        Write,
        Read
    }

測試程式碼

               {
                    EFCoreDbContext context = EFCoreContextFactory.createDbContext(WriteOrRead.Read);
                    UserInfo user = context.UserInfo.Find(2);
                }
                {
                    EFCoreDbContext context = EFCoreContextFactory.createDbContext(WriteOrRead.Read);
                    UserInfo user = context.UserInfo.Find(2);
                }
                {
                    EFCoreDbContext context = EFCoreContextFactory.createDbContext(WriteOrRead.Read);
                    UserInfo user = context.UserInfo.Find(2);
                }
                {
                    EFCoreDbContext context = EFCoreContextFactory.createDbContext(WriteOrRead.Read);
                    UserInfo user = context.UserInfo.Find(2);
                }