将 Env Conn 字符串注入到 .NET Core 2.0 w/EF Core DbContext 中与 Startup prj & 不同的类库中实现 IDesignTimeDbContextFactory [英] Injecting Env Conn String into .NET Core 2.0 w/EF Core DbContext in different class lib than Startup prj & implementing IDesignTimeDbContextFactory
问题描述
老实说，我无法相信这有多难......首先是我要达到的要求:
I honestly cannot believe how hard this is...first off the requirements that I am going for:
- 实施实体框架核心 2.0'
IDesignTimeDbContextFactory即 IDbContextFactory 重命名，以减少开发人员对其功能的混淆 - 我不想多次加载
appsettings.json.一个原因是因为我的迁移在MyClassLibrary.Data的域中运行，并且该类库中没有appsettings.js文件，我必须复制到输出目录appsettings.js.另一个原因是它不够优雅.
- Implementing Entity Framework Core 2.0'
IDesignTimeDbContextFactorywhich is IDbContextFactory renamed to be less confusing to developers as to what it does - I do not want to have to do loading of
appsettings.jsonmore than once. One reason is because my migrations are running in the domain ofMyClassLibrary.Dataand there is noappsettings.jsfile in that class library, I would have to toCopy to Output Directoryappsettings.js. Another reason is that it just not very elegant.
所以这是我目前有效的:
So here is what I have that currently works:
using System;
using Microsoft.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore.Design;
using Microsoft.Extensions.Configuration;
using AppContext = Tsl.Example.Data.AppContext;
namespace Tsl.Example
{
public class DesignTimeDbContextFactory : IDesignTimeDbContextFactory<AppContext>
{
public AppContext CreateDbContext(string[] args)
{
string basePath = AppDomain.CurrentDomain.BaseDirectory;
string envName = Environment.GetEnvironmentVariable("ASPNETCORE_ENVIRONMENT");
IConfigurationRoot configuration = new ConfigurationBuilder()
.SetBasePath(basePath)
.AddJsonFile("appsettings.json")
.AddJsonFile($"appsettings.{envName}.json", true)
.Build();
var builder = new DbContextOptionsBuilder<AppContext>();
var connectionString = configuration.GetConnectionString("DefaultConnection");
builder.UseMySql(connectionString);
return new AppContext(builder.Options);
}
}
}
这是我的 Program.cs:
And here is my Program.cs:
using System.IO;
using System.Reflection;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.Logging;
namespace Tsl.Example
{
public class Program
{
public static void Main(string[] args)
{
BuildWebHost(args).Run();
}
//public static IWebHost BuildWebHost(string[] args) =>
// WebHost.CreateDefaultBuilder(args)
// .UseStartup<Startup>()
// .Build();
/// <summary>
/// This the magical WebHost.CreateDefaultBuilder method "unboxed", mostly, ConfigureServices uses an internal class so there is one piece of CreateDefaultBuilder that cannot be used here
/// https://andrewlock.net/exploring-program-and-startup-in-asp-net-core-2-preview1-2/
/// </summary>
/// <param name="args"></param>
/// <returns></returns>
public static IWebHost BuildWebHost(string[] args)
{
return new WebHostBuilder()
.UseKestrel()
.UseContentRoot(Directory.GetCurrentDirectory())
.ConfigureAppConfiguration((hostingContext, config) =>
{
IHostingEnvironment env = hostingContext.HostingEnvironment;
config.AddJsonFile("appsettings.json", optional: true, reloadOnChange: true)
.AddJsonFile($"appsettings.{env.EnvironmentName}.json", optional: true, reloadOnChange: true);
if (env.IsDevelopment())
{
var appAssembly = Assembly.Load(new AssemblyName(env.ApplicationName));
if (appAssembly != null)
{
config.AddUserSecrets(appAssembly, optional: true);
}
}
config.AddEnvironmentVariables();
if (args != null)
{
config.AddCommandLine(args);
}
})
.ConfigureLogging((hostingContext, logging) =>
{
logging.AddConfiguration(hostingContext.Configuration.GetSection("Logging"));
logging.AddConsole();
logging.AddDebug();
})
//.UseIISIntegration()
.UseDefaultServiceProvider((context, options) =>
{
options.ValidateScopes = context.HostingEnvironment.IsDevelopment();
})
.UseStartup<Startup>()
.Build();
}
}
}
这是我的 Startup.cs:
And here is my Startup.cs:
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.DependencyInjection;
using ServiceStack;
using Tsl.Example.Interfaces;
using Tsl.Example.Provider;
using AppContext = Tsl.Example.Data.AppContext;
namespace Tsl.Example
{
public class Startup
{
// This method gets called by the runtime. Use this method to add services to the container.
public void ConfigureServices(IServiceCollection services)
{
services.AddTransient<IAppContext, AppContext>();
services.AddTransient<IExampleDataProvider, ExampleDataProvider>();
}
public void Configure(IApplicationBuilder app, IHostingEnvironment env)
{
if (env.IsDevelopment())
{
app.UseDeveloperExceptionPage();
}
app.UseServiceStack(new AppHost());
}
}
}
我想做的是使用 IOptions 模式，所以我创建了这个类:
What I would like to do is use the IOptions pattern, so I created this class:
namespace Tsl.Example
{
/// <summary>
/// Strongly typed settings to share in app using the .NET Core IOptions pattern
/// https://andrewlock.net/how-to-use-the-ioptions-pattern-for-configuration-in-asp-net-core-rc2/
/// </summary>
public class AppSettings
{
public string DefaultConnection { get; set; }
}
}
将此行添加到 Startup.ConfigureServices:
services.Configure<AppSettings>(options => Configuration.GetSection("AppSettings").Bind(options));
然后尝试将我的 IDesignTimeDbContextFactory 实现更改为:
And then tried and change my implementation of IDesignTimeDbContextFactory<AppContext> to:
public class DesignTimeDbContextFactory : IDesignTimeDbContextFactory<AppContext>
{
private readonly AppSettings _appSettings;
public DesignTimeDbContextFactory(IOptions<AppSettings> appSettings)
{
this._appSettings = appSettings.Value;
}
public AppContext CreateDbContext(string[] args)
{
var builder = new DbContextOptionsBuilder<AppContext>();
builder.UseMySql(_appSettings.DefaultConnection);
return new AppContext(builder.Options);
}
}
不幸的是，这不起作用，因为未注入 public DesignTimeDbContextFactory(IOptions 构造函数的 Ioptions 参数.我认为这是因为 IDesignTimeDbContextFactory 的实现在设计时被调用，而依赖注入在 .NET Core 应用程序中在设计时还没有准备好"?
Unfortunately this did not work because the Ioptions<AppSettings> argument of public DesignTimeDbContextFactory(IOptions<AppSettings> appSettings) constructor is not injected. I assume this is because implementations of IDesignTimeDbContextFactory<AppContext> are called at Design time and dependency injection is just not "ready" in .NET Core apps at design time?
我认为使用实现 IDesignTimeDbContextFactory 的 Entity Framework Core 2.0 模式注入特定于环境的连接字符串如此困难，而且不必复制和加载设置文件，这有点奇怪喜欢 appsettings.json 不止一次.
I think it is kind of strange that it is so hard to inject an environment specific connection string using the Entity Framework Core 2.0 pattern of implementing IDesignTimeDbContextFactory, and also not having to copy and load settings files like appsettings.json more than once.
推荐答案
如果您正在寻找从 appsettings.json 文件初始化的自定义设置类中获取数据库连接字符串的解决方案 - 这就是方法你可以这样做.不幸的是，您无法通过 DI 将 IOptions 注入您的 IDesignTimeDbContextFactory 实现构造函数.
If you are looking for solution to get database connection string from your custom settings class initialized from appsettings.json file - that is how you can do this. Unfortunatelly you can't inject IOptions via DI to your IDesignTimeDbContextFactory implementation constructor.
public class DesignTimeDbContextFactory : IDesignTimeDbContextFactory<AppContext>
{
public AppContext CreateDbContext(string[] args)
{
// IDesignTimeDbContextFactory is used usually when you execute EF Core commands like Add-Migration, Update-Database, and so on
// So it is usually your local development machine environment
var envName = Environment.GetEnvironmentVariable("ASPNETCORE_ENVIRONMENT");
// Prepare configuration builder
var configuration = new ConfigurationBuilder()
.SetBasePath(Path.Combine(Directory.GetCurrentDirectory()))
.AddJsonFile("appsettings.json", optional: false)
.AddJsonFile($"appsettings.{envName}.json", optional: false)
.Build();
// Bind your custom settings class instance to values from appsettings.json
var settingsSection = configuration.GetSection("Settings");
var appSettings = new AppSettings();
settingsSection.Bind(appSettings);
// Create DB context with connection from your AppSettings
var optionsBuilder = new DbContextOptionsBuilder<AppContext>()
.UseMySql(appSettings.DefaultConnection);
return new AppContext(optionsBuilder.Options);
}
}
当然，在您的 AppSettings 类和 appsettings.json 中，您可以有更复杂的构建连接字符串的逻辑.例如，像这样:
Of course in your AppSettings class and appsettings.json you could have even more sophisticated logic of building the connection string. For instance, like this:
public class AppSettings
{
public bool UseInMemory { get; set; }
public string Server { get; set; }
public string Port { get; set; }
public string Database { get; set; }
public string User { get; set; }
public string Password { get; set; }
public string BuildConnectionString()
{
if(UseInMemory) return null;
// You can set environment variable name which stores your real value, or use as value if not configured as environment variable
var server = Environment.GetEnvironmentVariable(Host) ?? Host;
var port = Environment.GetEnvironmentVariable(Port) ?? Port;
var database = Environment.GetEnvironmentVariable(Database) ?? Database;
var user = Environment.GetEnvironmentVariable(User) ?? User;
var password = Environment.GetEnvironmentVariable(Password) ?? Password;
var connectionString = $"Server={server};Port={port};Database={database};Uid={user};Pwd={password}";
return connectionString;
}
}
仅存储在 appsettings.json 中的值:
{
"Settings": {
"UseInMemory": false,
"Server": "myserver",
"Port": "1234",
"Database": "mydatabase",
"User": "dbuser",
"Password": "dbpassw0rd"
}
}
密码和用户存储在环境变量中:
With password and user stored in environment variables:
{
"Settings": {
"UseInMemory": false,
"Server": "myserver",
"Port": "1234",
"Database": "mydatabase",
"User": "MY-DB-UID-ENV-VAR",
"Password": "MY-DB-PWD-ENV-VAR"
}
}
在这种情况下，您应该这样使用它:
In this case you should use it this way:
// Create DB context with connection from your AppSettings
var optionsBuilder = new DbContextOptionsBuilder<AppContext>();
if(appSettings.UseInMemory) {
optionsBuilder = appSettings.UseInMemory
? optionsBuilder.UseInMemoryDatabase("MyInMemoryDB")
: optionsBuilder.UseMySql(appSettings.BuildConnectionString());
return new AppContext(optionsBuilder.Options);
这篇关于将 Env Conn 字符串注入到 .NET Core 2.0 w/EF Core DbContext 中与 Startup prj & 不同的类库中实现 IDesignTimeDbContextFactory的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
