如何从Blazor .NET Core项目连接到多个数据库? [英] How can I connect to multiple databases from a Blazor .NET Core project?

问题描述

如何从Blazor WebAssembly项目连接到多个数据库实例，在该项目中我还添加了托管的ASP.NET Core?

How do I connect to multiple database instances from a Blazor WebAssembly project, where I have also added the ASP.NET Core hosted?

我的想法是将 DBContexts 初始化为"Startup.cs"(来自Blazor.Server应用程序，该应用程序引用了Blazor.Client应用程序):

My thought was to initiate the DBContexts into the `Startup.cs`` (from Blazor.Server Application which has a reference to Blazor.Client Application):

public void ConfigureServices(IServiceCollection services)
{
    services.AddDbContext<DatabaseContext>(options =>
            options.UseSqlite(
                "connection string holder ..."));
}

像这样，但是我想让用户在我的视图中选择是否要对将在其中创建SQLite数据库实例的App进行测试运行.常规运行将是SQL Server数据库的一个实例.如何在ConfigureServices方法中执行此操作?

like this but I want to let the user choose in my View if they want to do a test run of the App where the SQLite database instance will be created. The regular run will be an instance to SQL Server database. How can I do this in the ConfigureServices method?

现在我正在构建 DBContexts 类，这些类也会影响吗?

Right now I am building the DBContexts classes, are these effected too?

控制器尚未完成，ASP.NET Core MVC控制器是正确的选择吗?

The controllers are not done yet, are ASP.NET Core MVC controllers the right choice?

推荐答案

您可以使用2个数据库上下文，一个接口和一项从API请求中发送的数据中选择上下文的服务来实现该目标:

You can implement that using 2 DB contexts, one interface and a service choosing the context from data sent in API requests:

数据库上下文界面

public interface IDatabaseContext
{
// add all DbSet declaration here
}

数据库上下文

public class DatabaseContext : IDatabaseContext
{
// db context implementation
}

测试数据库上下文

public class TestDatabaseContext: DatabaseContext
{
// add your constructor
}

DbContext解析器服务

public class DbContextResolver
{
    public bool IsTest { get; set; }

服务器端DI设置

services.AddDbContext<DatabaseContext>(options =>
            options.UseSqlServer(
                "SqlServer connection string holder ..."))
        .AddDbContext<TestDatabaseContext>(options =>
            options.UseSqlite(
                "Sqlite connection string holder ..."))
        .AddScoped<DbContextResolver>())
        .AddScoped<IDatabaseContext>(p =>
        {
            var resolver = p.GetRequiredService<DbContextResolver>();
            if (resolver.IsTest)
            {
                retrun p.GetRequiredService<TestDatabaseContext>();
            }
            return p.GetRequiredService<DatabaseContext>();
        }));

从请求中选择数据库上下文

public void Configure(IApplicationBuilder app)
{
     app.Use((context, next) =>
     {
          var resolver = context.RequestServices.GetRequiredService<DbContextResolver>();
          resolver.IsTest = context.Request.Query.ContainsKey("test"); // here the context is choosed by query string but you can choose to send an header instead
          return next();
     }
}

在控制器或服务中使用所选的数据库上下文

public class MyController : Controller
{
     public MyController(IDatabaseContext context)
...
}

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