Powershell 2.0 - 传递给函数时关闭SqlDataReader

Question

我正在与一组使用Powershell 2.0的自定义.Net 2.0程序集进行交互,以自动执行当前任务.我加载所有必需的dll并在dll中调用DAL方法来检索System.Data.SqlDataReader.当我将SqlDataReader传递到同一个自定义程序集中的构造函数时,我收到"在读取器关闭时无效尝试调用HasRows".例外.

代码示例:

dir D:\stuff\*.dll | foreach { [Reflection.Assembly]::LoadFrom($_.FullName) } | out-null
[CustomAssembly.DataConfig]::ConnectionString = "Valid Connection String"
$reader=[CustomAssembly.DAL.Thing]::Get(123)
new-object CustomAssembly.BusinessObjects.Thing($reader)

在我调用Thing构造函数之前,$ reader是打开的,并且有数据.

我必须遗漏一些东西,但我不确定它是什么.

编辑1:

$ reader在传递给函数,powershell或程序集中的任何时候似乎都被读取和关闭.有办法防止这种情况吗？

编辑2:

Powershell自动展开再次打击

如何阻止PowerShell解压缩Enumerable对象？

PowerShell函数中的奇怪行为返回DataSet/DataTable

以下修改的代码示例通过将结果包装在单个元素数组中来工作,因此自动展开不会影响SqlDataReader.请注意"$ reader ="语句后面的单个逗号.那不是拼写错误.

dir D:\stuff\*.dll | foreach { [Reflection.Assembly]::LoadFrom($_.FullName) } | out-null
[CustomAssembly.DataConfig]::ConnectionString = "Valid Connection String"
$reader=,[CustomAssembly.DAL.Thing]::Get(123)
new-object CustomAssembly.BusinessObjects.Thing($reader)

Answer 1

我前段时间遇到过类似的问题.看看这段代码:

我创建了自己的Enumerator,它打印了一些关于何时调用它的信息.它与你的SqlDataReader(我认为)实现的IEnumerator一样.

PS> Add-Type -TypeDefinition @"
    using System;
    using System.Collections;
    public class MyEnumerator2 : IEnumerator
    {
        private int _count = 10;
        private Random r = new Random();

        public MyEnumerator2(int count)
        {
            _count = count;
        }

        public bool MoveNext()
        {
            Console.WriteLine("Moving!");
            _count--;
            return _count >= 0;
        }

        public void Reset()
        {
            throw new NotImplementedException();
        }

        public object Current
        {
            get
            {
                Console.WriteLine("Current!");
                return r.Next();
            }
        }
    }
"@

然后让我们创建一个类型的对象并尝试输出它:

PS> $mye = New-Object MyEnumerator2 5
PS> $mye | % -begin { write-host 'starting' } -Process { write-host 'next is ' $_ }
starting
Moving!
Current!
next is  2081278528
Moving!
Current!
next is  2000135673
Moving!
Current!
next is  692162542
Moving!
Current!
next is  1531746038
Moving!
Current!
next is  1550381634
Moving!

一切都如预期.但现在

PS> function iteratemye($o) {
    $o | % -begin { write-host 'starting' } -Process { write-host 'next is ' $_ }
}
PS> $mye = New-Object MyEnumerator2 5
PS> iteratemye $mye
Moving!
Current!
Moving!
Current!
Moving!
Current!
Moving!
Current!
Moving!
Current!
Moving!
starting
Moving!

如果将此枚举器传递给函数,则会在它到达正文之前将其读取.那太糟糕了.

所以看看你的代码.如果你使用像我iteratemye这样的功能,那就是问题的原因.

更新:它没有实现IEnumerator,但是IEnumerable.我看到你只是将对象传递给一些构造函数,这与我遇到的问题不同,但我相信PowerShell仍会尝试获取枚举器并做一些魔术.