C#：使用实体框架代码优先访问数据库

Question

我是 ASP.NET MVC 的初学者，并尝试使用 Entity Framework Code-First 进行数据库访问，但出现错误。我在 stackoverflow 上看到了很多问题，但它们与我的情况无关。我的错误是。

EntityFramework.dll 中出现“System.InvalidOperationException”类型的异常，但未在用户代码中处理

附加信息：无法完成操作。提供的 SqlConnection 未指定初始目录或 AttachDBFileName。

在 LensStoreController.cs 中 var brands = lensStoreDB.Brands.ToList(); 行

LensStoreController.cs

public ActionResult Index()
{
    var brands = lensStoreDB.Brands.ToList();
    return View(brands);
}

Brands.cs、Lenses.cs 和 Manufacturer.cs 是我的模型类

品牌.cs

using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.Linq;
using System.Web;

namespace EyeContactLens.Models
{
    public class Brands
    {
        [Key]
        public int BrandId { get; set; }
        public string Name { get; set; }
        public string Description { get; set; }
        public List<Lenses> Lenses { get; set; }

    }

}

镜头.cs

using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.Linq;
using System.Web;

namespace EyeContactLens.Models
{
    public class Lenses
    {
        [Key]
        public int LensesId { get; set; }
        public int BrandId { get; set; }
        public int ManufacturerId { get; set; }
        public string Title { get; set; }
        public decimal Price { get; set; }
        public string LensManuUrl { get; set; }
        public Brands Brand { get; set; }
        public Manufacturer Manufacturer { get; set; }
    }
}

制造商.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;

namespace EyeContactLens.Models
{
    public class Manufacturer
    {
        public int ManufacturerId { get; set; }
        public string Name { get; set; }
    }
}

我还有一个班级SampleData.cs，我想在浏览器上显示其数据。

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Data.Entity;

namespace EyeContactLens.Models
{
    public class SampleData : DropCreateDatabaseIfModelChanges<EyeContactLensEntities>
    {
        protected override void Seed(EyeContactLensEntities context)
        {
            var brands = new List<Brands>
            {
                new Brands { Name = "Cooper Vision"},
                new Brands { Name = "Fresh Kon"},
                new Brands { Name = "Flexcon"},
                new Brands { Name = "Avaira"},
            };

            var manufacturer = new List<Manufacturer>
            {
                 new Manufacturer { Name = "Oculus"},
                 new Manufacturer { Name = "Alcon (CIBA Vision)"}
            };

            new List<Lenses>
            {
                new Lenses { Title = "Biofinity Contact Lens", Brand = brands.Single(b => b.Name == "Cooper Vision"), Price = 8.99M, Manufacturer = manufacturer.Single(a => a.Name == "Alcon (CIBA Vision)"), LensManuUrl = "/Content/Images/placeholder.gif" },
                new Lenses { Title = "FreshKon A55", Brand = brands.Single(b => b.Name == "Fresh Kon"), Price = 18.99M, Manufacturer = manufacturer.Single(a => a.Name == "Oculus"), LensManuUrl = "/Content/Images/placeholder.gif" },
                new Lenses { Title = "Flexcon Blue Tint UV Prolong wear (BUPW) (45%)", Brand = brands.Single(b => b.Name == "Flexcon"), Price = 81.99M, Manufacturer = manufacturer.Single(a => a.Name == "Oculus"), LensManuUrl = "/Content/Images/placeholder.gif" },
                new Lenses { Title = "Frequency 55 Toric Contact Lens", Brand = brands.Single(b => b.Name == "Cooper Vision"), Price = 10.99M, Manufacturer = manufacturer.Single(a => a.Name == "Alcon (CIBA Vision)"), LensManuUrl = "/Content/Images/placeholder.gif" },
                new Lenses { Title = "Freshkon N-Hance Toric", Brand = brands.Single(b => b.Name == "Fresh Kon"), Price = 11.99M, Manufacturer = manufacturer.Single(a => a.Name == "Oculus"), LensManuUrl = "/Content/Images/placeholder.gif" }
            }.ForEach(a => context.Lenses.Add(a));
        }
    }
}

我也使用EyeContactLensEntities.cs 作为DbContext：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Data.Entity;

namespace EyeContactLens.Models
{
    public class EyeContactLensEntities : DbContext
    {
        public DbSet<Lenses> Lenses { get; set; }
        public DbSet<Brands> Brands { get; set; }
    }
}

web.config:

<connectionStrings>
    <add name="EyeContactLensEntities" connectionString="Data Source=|DataDirectory|EyeContactLens.sdf" providerName="System.Data.SqlClient"/>
</connectionStrings>

Global.asax.cs

protected void Application_Start()
{
    System.Data.Entity.Database.SetInitializer(new Models.SampleData());

    AreaRegistration.RegisterAllAreas();
    FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
    RouteConfig.RegisterRoutes(RouteTable.Routes);
    BundleConfig.RegisterBundles(BundleTable.Bundles);
}

Answer 1

您的连接字符串错误。 您需要在配置字符串中提供的内容是数据源（例如 SQL Server 实例）和初始目录（例如该服务器上的数据库）。

可以使用 Sql Server Management Studio 打开一个 .sdf，从那里您应该能够看到您需要连接的具体内容。

编辑： 有关如何使用 SQL Server Management Studio 执行此操作的链接： How do you open an SDF file (SQL Server Compact Edition)?

Answer 2

您需要更改连接字符串中的 providerName：

<connectionStrings>
    <add name="EyeContactLensEntities" 
         connectionString="Data Source=|DataDirectory|EyeContactLens.sdf" 
         providerName="System.Data.SqlSqlServerCe.4.0"/>
</connectionStrings>

并且您需要安装 SQL Server Compact EF Nuget 包：

Install-Package EntityFramework.SqlServerCompact