从Entity Framework Core中的cookie和基本路径创建数据库上下文

debugcn 发表于 Dev

安德鲁斯

Postgres数据库具有多个方案，例如company1，company2，... companyN

浏览器发送包含方案名称的cookie。数据访问操作应在此方案中发生。Web应用程序用户可以选择不同的方案。在这种情况下，将设置不同的cookie值。

使用了Npgsql EF核心数据提供程序。

ASP NET MVC 5 Core应用程序在StartUp.cs中注册了工厂：

    public void ConfigureServices(IServiceCollection services)
    {
        services.AddHttpContextAccessor();
        services.AddScoped<IEevaContextFactory, EevaContextFactory>();
      ....

家庭控制器尝试使用它：

public class HomeController : EevaController
{
    public ActionResult Index()
    {
        var sm = new SchemeManager();
        sm.PerformInsert();
    ....

由于工厂成员为null，因此将引发异常。如何解决呢？

public interface IEevaContextFactory
{
    EevaContext Create();
}

public class EevaContextFactory : IEevaContextFactory
{
    private IHttpContextAccessor httpContextAccessor;
    private IConfiguration configuration;

    public EevaContextFactory(IHttpContextAccessor httpContextAccessor, IConfiguration configuration)
    {
        this.httpContextAccessor = httpContextAccessor;
        this.configuration = configuration;
    }

    public EevaContext Create()
    {
        var builder = new DbContextOptionsBuilder<EevaContext>();
        var pathbase = httpContextAccessor.HttpContext.Request.PathBase.Value;
        var scheme = httpContextAccessor.HttpContext.Request.Cookies["Scheme"];

        var csb = new NpgsqlConnectionStringBuilder()
        {
            Host = pathbase,
            SearchPath = scheme
        };
        builder.UseNpgsql(csb.ConnectionString);
        return new EevaContext(builder.Options);
    }
}

方案数据访问方法：

public class SchemeManager
{
    readonly IEevaContextFactory factory;

    public SchemeManager(IEevaContextFactory factory)
    {
        this.factory = factory;
    }

    public SchemeManager()
    {
    }

    public void PerformInsert()
    {
        using (var context = factory.Create())
        {
            var commandText = "INSERT into maksetin(maksetin) VALUES (CategoryName)";
            context.Database.ExecuteSqlRaw(commandText);
        }
    }
}

尼尔·W

var sm = new SchemeManager()

...将在SchemeManager上调用无参数构造函数，因此不会注入IEevaContextFactory。您应该将工厂注入控制器，然后将其传递给SchemeManager。

删除您的无参数构造函数。不需要

public class HomeController : EevaController
{
    private IEevaContextFactor eevaFactory;
           
    public HomeController(IEevaContextFactory factory)
    {
         eevaFactory = factory;
    }
        
    public ActionResult Index()
    {
         var sm = new SchemeManager(eevaFactory);
         sm.PerformInsert();
         ....
    }
}

您的另一个选择是将SchemeManager放入DI容器中，然后DI容器将在构造函数上自动解析IEevaContextFactory，然后将SchemeManager注入到您的控制器中。

无论哪种方式，都删除该无参数的构造函数。

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