ENTITYFRAMEWORKCORE 二使用配置文件来配置数据库链接

首先 配置文件现在已经变成appsettings.json，

先添加一个连接字符串

 "ConnectionStrings": {
    "PWDatabase": "Data Source=172.28.8.120;Initial Catalog=WebPW;User ID=sa;Password=Windows2008;"
  }

然后 修改Startup.cs 的ConfigureServices方法。

将以前的代码

   services.AddDbContext<WebPWContext>();

修改为

 public void ConfigureServices(IServiceCollection services)
        {
            // Add framework services.
            services.AddDbContext<WebPWContext>(options =>
        options.UseSqlServer(Configuration.GetConnectionString("PWDatabase")));
            services.AddMvc();
        }

需要添加引用

using Microsoft.EntityFrameworkCore;

然后修改 生成的“***Context.cs”文件 

删掉下面的方法， 

   protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {
#warning To protect potentially sensitive information in your connection string, you should move it out of source code. See http://go.microsoft.com/fwlink/?LinkId=723263 for guidance on storing connection strings.
           optionsBuilder.UseSqlServer(@"Data Source=172.28.8.120;Initial Catalog=WebPW;User ID=sa;Password=Windows2008");
          
        }

添加方法

  public WebPWContext(DbContextOptions<WebPWContext> options)
            : base(options)
        { }

参考文档 https://docs.efproject.net/en/latest/platforms/aspnetcore/existing-db.html