我试图让EF 5.0 code第一次使用的PostgreSQL（Npgsql提供商）。我有Npgsql 2.0.12.1通过的NuGet安装（引用的程序集是2.0.12.0虽然）。 我有Npgsql中的app.config声明（包括默认连接工厂和供应商的工厂）：

I'm trying to get EF 5.0 code first working with PostgreSQL (Npgsql provider). I have Npgsql 2.0.12.1 installed via NuGet (referenced assembly is 2.0.12.0 though). I have Npgsql declared in app.config (both default connection factory and provider factory):

<entityFramework>   
    <defaultConnectionFactory type="Npgsql.NpgsqlFactory, Npgsql, Version=2.0.12.0, Culture=neutral, PublicKeyToken=5d8b90d52f46fda7" />
 </entityFramework>
 <system.data>
        <DbProviderFactories>
          <add name="Npgsql Data Provider"
                invariant="Npgsql"
                description="Data Provider for PostgreSQL"
                support="FF"
                type="Npgsql.NpgsqlFactory, Npgsql, Version=2.0.12.0, Culture=neutral, PublicKeyToken=5d8b90d52f46fda7"/>
        </DbProviderFactories>
 </system.data>

我有以下的测试运行成功：

I have following test running successfully :

[Test]
public void DatabaseConnection_DatabaseFactoryTest()
{
    var factory = DbProviderFactories.GetFactory("Npgsql");
    var conn = factory.CreateConnection();
    conn.ConnectionString = _connectionString;
    var npg = (NpgsqlConnection)conn;
    var result = TestConnectionHelper(npg); // scalar select version(), nothing particular
    Assert.AreEqual(result, "PostgreSQL 9.2.2, compiled by Visual C++ build 1600, 64-bit");            
}

这意味着至少有数据库实例运行，并提供配置成功。 现在，我想是使用自定义的数据库上下文从的DbContext继承，将通过连接字符串来连接到相同的提供者和初始化的：

That means at least database instance is running and provider is configured successfully. Now what i want is to use custom database context inherited from DbContext which will be tied to same provider and initialized via connection string :

public class InventoryContext : DbContext
{
    public InventoryContext(string nameOrConnectionString) : base(nameOrConnectionString)
    {
    }
    // mappings and properties, cut for conciseness
}

下面的测试失败：

Following test fails :

[Test]
public void DatabaseConnection_DatabaseContextTest()
{
    using (var ctx = new InventoryContext(_connectionString))
    {
        //var db = ctx.Database;
        ctx.InventoryObjects.Add(_inventoryObject); // exception here
        ctx.SaveChanges();
    }
}   

报告说，

Failed to set Database.DefaultConnectionFactory to an instance of the 'Npgsql.NpgsqlFactory, Npgsql, Version=2.0.12.0, Culture=neutral, PublicKeyToken=5d8b90d52f46fda7' type as specified in the application configuration. See inner exception for details.

内部异常是出现InvalidOperationException：

Inner exception is InvalidOperationException :

{"Constructor for type \"Npgsql.NpgsqlFactory\" is not found."}

我想有一个与连接字符串的问题（不包含Npgsql提供商）：

I guess there is a problem with connection string (it does not contain Npgsql provider) :

"Server=127.0.0.1;Port=5432;User Id=postgres;Password=p4ssw0rd;Database=InventoryDatabase;";

什么是最优雅的方式以编程方式解决这个问题？刚试过路过的connectionString从app.config中上下文的构造，它的工作原理。 修改 上传的测试项目，Dropbox的 - VS2012的解决方案，10 MB

What is the most elegant way to solve this problem programmatically? Just tried passing connectionString from app.config to context's constructor, it works. edit Uploaded test project to Dropbox - VS2012 solution, 10 mb

推荐答案

更​​深入地挖掘问题，发现它是由这一事实，Npgsql所引用的EntityFramework 4.4.0组装。解决如下：

Dug deeper into the problem, found out that it is caused by that fact that Npgsql is referencing EntityFramework 4.4.0 assembly. Solved as follows :

新增EF的NuGet包测试项目（这是建立对FW 4.5）; 在Npgsql2010项目中手动添加引用EntityFramework.dll 5版本（的NuGet增加了4.4.0默认情况下）; 改变组件Npgsql的app.config绑定的的的EntityFramework，版本= 5.0.0.0，文化=中性公钥= b77a5c561934e089的; 修正通过构造公共上面的的构造类型Npgsql.NpgsqlFactory找不到的错误描述;

修正了以下错误的的无法投NpgsqlFactory到IDbConnectionFactory的通过实现IDbConnectionFactory接口NpgsqlFactory： Added EF Nuget package to test project (which is build against FW 4.5); Manually added reference to EntityFramework.dll version 5 in Npgsql2010 project (Nuget adds 4.4.0 by default); Changed assembly binding in Npgsql app.config to "EntityFramework, Version=5.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089"; Fixed described above "Constructor for type "Npgsql.NpgsqlFactory" is not found error by making constructor public;

Fixed following error "Unable cast NpgsqlFactory to IDbConnectionFactory" by implementing IDbConnectionFactory interface on NpgsqlFactory :

使用System.Data.Entity.Infrastructure; ... 公共密封类NpgsqlFactory：DbProviderFactory，IServiceProvider的，IDbConnectionFactory ... 公众的DbConnection创建连接（字符串nameOrConnectionString） {       返回新NpgsqlConnection（nameOrConnectionString）; } ð

using System.Data.Entity.Infrastructure; ... public sealed class NpgsqlFactory : DbProviderFactory, IServiceProvider, IDbConnectionFactory ... public DbConnection CreateConnection(string nameOrConnectionString) { return new NpgsqlConnection(nameOrConnectionString); } d

现在我遇到错误：3F000：模式DBO不存在，这是关系到EF。 （表名，大众），虽然modelBuilder.Entity（）ToTable：我已经映射到PostgreSQL标准的公共架构中的DbContext的OnModelCreating。期待这个问题的解决方案。

Now i'm experiencing "Error: 3F000: schema "dbo" doesn't exist" which is related to EF. I have mapping to PostgreSQL standard public schema in DbContext's OnModelCreating : modelBuilder.Entity().ToTable("TableName", "public") though. Looking forward to solution of this problem.