什么是using语句并添加一个参考值之间的差异？ [英] What's the difference between using statement and adding a reference?

问题描述

在Visual Studio中，当你有一个引用添加到一个dll？我总是有一个最低在我的项目引用，我尽量只包括那些真正需要的人。

In Visual Studio, when do you have to add a reference to a dll? I always try to have a minimum of references in my projects, I try to only include the ones that are really necessary.

我想我只需要一个引用我有一个使用语句在我的源代码。但是，这还不够。

I would think that I only need a reference if I have a using statement in my source. But that's not always enough.

比如说，我有一个非常简单的程序中使用系统和微软是。 Practices.EnterpriseLibrary.Data：

For instance, I have a very simple program that is using System and Microsoft.Practices.EnterpriseLibrary.Data:

using System;
using Microsoft.Practices.EnterpriseLibrary.Data;

public class SimpleConnection {
    private static void Main() {
        var database = DatabaseFactory.CreateDatabase();
        var command =
            database.GetSqlStringCommand(
                "select table_name from information_schema.tables");
        using (var reader = database.ExecuteReader(command)) {
            while (reader.Read()) {
                Console.WriteLine(reader.GetString(0));
            }
        }
    }
}

我会的认为的我只需要参考系统和Mi​​crosoft.P​​ractices.EnterpriseLibrary.Data。但事实并非如此。如果我不引用System.Data这，代码将无法编译。

I would think I only have to reference System and Microsoft.Practices.EnterpriseLibrary.Data. But that's not true. If I don't reference System.Data, the code won't compile.

类型
'System.Data这。 Common.DbCommand'是在装配不是引用
定义
。您必须添加一个引用
到组装'System.Data这，
版本2.0.0.0 =文化=中立，
公钥= b77a5c561934e089'。

The type 'System.Data.Common.DbCommand' is defined in an assembly that is not referenced. You must add a reference to assembly 'System.Data, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089'.

我怎么能事先知道，当我要补充的东西引用我不是使用？

How can I know beforehand when I have to add a reference to something I'm not using?

推荐答案

您必须添加一个引用到类驻留在装配和任何相关性，包括

You have to add a reference to an assembly the class resides in, and any dependencies, that includes

• 从其他组件的返回类型（即一个方法返回一个的DbCommand ）


• 基类或接口与其他组件（即一类从的DbCommand 派生或实现一个接口）

• return types from other assembly (ie. a method returns a DbCommand)
• base class or interface from other assembly (ie. a class derives from DbCommand or implements an interface)

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