奇怪的“未引用程序集"尝试调用有效方法重载时出错

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问题描述

我在 Assembly A 中使用方法重载:

I'm using method overloading in Assembly A:

public static int GetPersonId(EntityDataContext context, string name)
{
    var id = from ... in context... where ... select ...;
    return id.First(); 
}

public static int GetPersonId(SqlConnection connection, string name)
{
    using (var context = new EntityDataContext(connection, false))
    {
        return GetPersonId(context, name);
    }
}

当我尝试从 Assembly B 调用第二个重载时，VS 会产生以下编译时错误:

When I try to call the second overload from Assembly B, VS produces the following compile-time error:

类型System.Data.Entity.DbContext"在一个程序集中定义，该程序集没有被引用.您必须添加对程序集的引用'EntityFramework，版本=6.0.0.0，文化=中性，PublicKeyToken=...'.

The type 'System.Data.Entity.DbContext' is defined in an assembly that is not referenced. You must add a reference to assembly 'EntityFramework, Version=6.0.0.0, Culture=neutral, PublicKeyToken=...'.

Assembly B 引用 Assembly A.实体框架仅在 Assembly A 中引用，因为 Assembly B 不使用它.Assembly B 的调用如下所示:

Assembly B references Assembly A. Entity Framework is referenced only in Assembly A as Assembly B doesn't use it. The call from Assembly B looks like this:

using (SqlConnection connection = new SqlConnection(connectionString))
{
    connection.Open();                               
    var id = AssemblyA.GetPersonId(connection, name); // compiler error
    ...
}

我不明白的是，如果我将 Assembly A 中的方法签名 更改为例如:

What I don't understand is that the error goes away if I change the method signature in Assembly A to e.g.:

public static int GetPersonId(SqlConnection connection, string name, bool empty)

并将调用更改为:

var id = AssemblyA.GetPersonId(connection, name, true); // no error

为什么我的代码在第一种情况下没有编译?如错误所示，它似乎与实体框架无关.我一直认为 C# 允许方法重载，其中方法签名仅在参数类型上有所不同.例如.我可以按预期运行以下代码而不会出现问题:

Why is my code not compiling in the first case? It doesn't seem to be related to Entity Framework as the error indicates. I have always thought that C# allows method overloading where method signatures differ only in parameter types. E.g. I can run the following code without problems as expected:

static void DoStuff(int a, int b) { ... }
static void DoStuff(int a, float b) { ... }

DoStuff(10, 5);
DoStuff(10, 5.0f);

那么，尽管显然是合法的超载，为什么我的情况会出现错误?

So why am I getting the error in my situation despite the apparently legal overloads?

请注意，从 Assembly B 调用其他内部使用 EntityDataContext 的方法没有问题，唯一的区别是这些方法没有重载.

Note that from Assembly B I have no problems calling other methods that internally use EntityDataContext, the only difference is that these methods don't have overloads.

背景

EntityDataContext 继承 EF 的 DbContext:

public partial class EntityDataContext : DbContext
{
        public EntityDataContext() : base("name=EntityDataContext") { }

        public EntityDataContext(DbConnection connection, bool contextOwnsConnection) 
            : base(connection, contextOwnsConnection) { }

        ...
}

我首先将 .NET 4.0 和 EF 6 代码用于现有数据库，并添加了一些自定义 ctor 重载.

I'm using .NET 4.0 with EF 6 code first to an existing database with some custom ctor overloads added.

奇怪的“未引用程序集"尝试调用有效方法重载时出错

问题描述

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