在using语句使用不同类型（C＃） [英] using various types in a using statement (C#)

问题描述

由于using语句C＃是只是尝试语法糖/ {最终处置}为什么它接受多个对象，只有当他们是同一类型的吗？

Since the C# using statement is just a syntactic sugar for try/finally{dispose} why does it accept multiple objects ONLY IF THEY ARE OF THE SAME TYPE?

我不明白这一点，因为所有他们需要的是IDisposable接口。如果所有的人都实现IDisposable它应该是罚款，但事实并非如此。

I don't get it since all they need to be is IDisposable. If all of them implement IDisposable it should be fine but it isn't.

特别是我用来写

using (var cmd = new SqlCommand())
{
    using (cmd.Connection)
    {
        // code
    }
}

我压缩成：

using (var cmd = new SqlCommand())
using (cmd.Connection)
{
    // code
}

和我想进一步压缩成：

using(var cmd = new SqlCommand(), var con = cmd.Connection)
{
    // code
}

但我不能。我大概可以，有些人会说，写：

but I can't. I could probably, some would say, write :

using((var cmd = new SqlCommand()).Connection)
{
    // code
}

因为所有我需要处理的是连接而不是命令，但这是除了点。

since all I need to dispose is the connection and not the command but that's besides the point.

推荐答案

您虽然可以做到这一点：

You can do this though:

using (IDisposable cmd = new SqlCommand(), con = (cmd as SqlCommand).Connection)
{
   var command = (cmd as SqlCommand);
   var connection = (con as SqlConnection);
   //code
}

也许这将是你满意。

Perhaps that would be satisfactory to you.

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