Powershell 2.0 - Closing SqlDataReader when passed to a function

Question

I am interacting with a set of custom .Net 2.0 assemblies with Powershell 2.0 to automate the current task. I load all the necessary DLLs and call the DAL method in the dll to get System.Data.SqlDataReader. When I pass SqlDataReader to the constructor in the same assembly, I get an "Invalid attempt to call HasRows when the reader is closed." an exception.

Code example:

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) 

The $ reader is open and has data before I call the Thing constructor.

Something is missing me, but I'm not sure what it is.

Change 1:

The $ reader is read and closed when it is passed to the function, in powershell or in the assembly. Is there any way to prevent this?

Edit 2:

PowerShell auto-punch strikes again

How to stop PowerShell from unpacking an Enumerable object?

Strange PowerShell behavior returning a DataSet / DataTable

The following modified code example works by wrapping the result in a single array of elements, so automatic deployment does not affect SqlDataReader. Note the single comma after the $ reader = operator. This is not a typo.

 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

I ran into similar problems a while ago. Take a look at this code:

I create my own Enumerator that prints some information about when it is called. Same as your SqlDataReader , which (I think) implements IEnumerator .

 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(); } } } "@ 

Then create an object of type and try to output it:

 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! 

Everything is as expected. But now

 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! 

If you pass this enumerator to a function, it will be read before it reaches the body . This is very bad.

So take a look at your code. If you use some feature like my iteratemye , this is the cause of your problems.

Update: it does not implement IEnumerator , but IEnumerable . I see that you are simply passing the object to some constructor, which is not the same problem as mine, but I believe that PowerShell will still try to get the enumerator and do some magic.