I have a problem when using nested loops in my Control Flow. The package contains an outer Foreach Loop using the Foreach File Enumerator which in my test case will loop over two files found in a directory. Inside this loop is another Foreach Loop using the Foreach Nodelist Enumerator. Before entering the inner loop a variable, xpath, is set to a value that depends on the current file, i e /file[name = '@.CurrentFileName']/content. The Nodelist Enumerator is set to use this variable as its OuterXPATHString. Now, this is what happens:
First Iteration:
The first file is found and the value of xpath = /file[name = 'test1.txt']/content. When the inner loop is entered it iterates over the content elements under the file with name test1.txt as expected.
Second Iteration:
The second file is found and the value of xpath = /file[name = 'test2.txt']/content. When the inner loop is entered it unexpectedly still iterates over the content elements under the file with name test1.txt.
My question is: Should it not be possible to change the loop condition of an inner loop in an outer loop such that the next time it is entered it will be done based on the new condition? It seems that the xpath variable is read once, the first time, and never again. If that is the case, does anyone know of a workaround?
Regards,
Lars R?nnb?ck
I noticed that you can set which enumerator to use on the Foreach Loop container using an Expression. On the off chance that this will cause the enumerator to reload at the start of the container and thereby solving my problem described above I thought I'd try it, but I cannot find what value Foreach Enumerator should be set to. It won't accept the string Foreach NodeList Enumerator as a string with or without quotation marks, neither the number 6 works, which seems to be the index of the enumerator in the drop down list. If anyone knows how to set this, let me know and I will try it.
Edit: After reading Kirks blog on Expressions: Part III it seems that expressions applied to Foreach Enumerators are evaluated Before Saving, After Loading, Before Initialization and Before returning from GetEnumerator calls. I am guessing that GetEnumerator is called only once, which causes the behaviour above. I desperately need a workaround then.
Regards,
Lars R?nnb?ck
On what property of the inner loop nodelist enumerator is the property expression set?
You can't set the enumerator to use with an expression. Expressions don't understand objects or IDispatch, so they cannot provide an enumerator to the foreach loop.
It sounds to me like you may have the property expression on the wrong property of the Nodelist Enumerator.
Can you post the package on
http://lab.msdn.microsoft.com/productfeedback/default.aspx
We can take a look. I also have a sneaking suspicion that you've found a bug.
K
|||I'll try to give you more detailed information. The settings for the inner Foreach Loop are (in three different variations that all produce the same result):
Variation 1:
In the Collection settings:
Under Foreach Loop Editor the Foreach NodeList Enumerator is selected and no expressions are used here.
In the Enumerator Configuration DocumentSourceType is set to Variable and DocumentSource is set to User::FileDefinition which changes for each iteration of the outer loop. EnumerationType is NodeText, OuterXPathStringSourceType is DirectInput and OuterXPathSource is set to /file/content.
Nothing is set in the other sections.
This iterates over the first FileDefinition for both iterations of the outer loop, even though it is clearly different the second time the inner loop is reached.
Variation 2:
In the Collection settings:
Under Foreach Loop Editor the Foreach NodeList Enumerator is selected and no expressions are used here.
In the Enumerator Configuration DocumentSourceType is set to Variable and DocumentSource is set to User::FileDefinition which does not change and contains content for both example files. EnumerationType is NodeText, OuterXPathStringSourceType is Variable and OuterXPathSource is set to User::xpath. For User::xpath EvaluateAsExpression is set to True and the Expression is "/file[name = '" + @.CurrentFileName + "']/content", so that it will change with each iteration of the outer loop.
Nothing is set in the other sections.
This iterates over the first content (test1.txt) in the FileDefinition for both iterations of the outer loop.
Variation 3:
In the Collection settings:
Under Foreach Loop Editor the Foreach NodeList Enumerator is selected and an expression is set here for the OuterXPathString to be User::xpath.
In the Enumerator Configuration DocumentSourceType is set to Variable and DocumentSource is set to User::FileDefinition which does not change and contains content for both example files. EnumerationType is NodeText, OuterXPathStringSourceType is DirectInput and OuterXPathSource is set to an empty string. For User::xpath EvaluateAsExpression is set to True and the Expression is "/file[name = '" + @.CurrentFileName + "']/content", so that it will change with each iteration of the outer loop.
Nothing is set in the other sections.
This iterates over the first content (test1.txt) in the FileDefinition for both iterations of the outer loop.
Under the Expression settings for the Foreach Container there is a Property named ForeachEnumerator, which is the one I was referring to above, but I could not find a valid value for it. I have no idea if that would have helped in any way though.
For different reasons I cannot put the package on the feedback pages. I could provide it to you in confidence though. I can be reached through lars(at)delicate.se.
Thanks for the reply,
Lars
Kirk,
I managed to reproduce the problem with three new small packages, one for each variation described above. They are filed as a bug at http://lab.msdn.microsoft.com/ProductFeedback/viewFeedback.aspx?feedbackId=FDBK43839. I'm still hoping that it's me who has done something wrong though, since this is preventing me from finishing a step in our current project. Workarounds are welcome too ;)
Regards,
Lars
Thanks,
we were able to repro the problem.
The workaround will be to use to move the inner ForEach Loop to a child package
|||
Thanks Nick,
I've done that and it works as intended now. One pitfall to avoid though that took me a while to figure out, if you have package level event handlers in the parent package, they are still active when the tasks in the child package is running.
Regards,
Lars
Lars,
That's because child packages are just an extension of the parent's container hierarchy. All events "bubble-up" to the top of the container hierarchy unless System::Propogate=FALSE.
-Jamie
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