Archive for the ‘C#’ Category

Importing PowerShell Modules from GAC DLLS in order to use their CmdLets

What I am writing here is nothing new, just a consolidation of attempted answers I found when trying to do as the title of this post describes.  Now to set the stage, this is a DLL deployed as part of a SharePoint solution which is why it gets dropped to the GAC and then the CmdLets are used to configure the solution once the SharePoint WSPs are deployed.

Import-Module will take a full path to a DLL in the GAC or anywhere in order to use the CmdLets within it, but I didn’t want to be mucking with resolving the GAC path for a DLL, I just wanted to give it the assembly name without version and what not.  In looking at other people comments to loading DLLs with partial name, the obvious “LoadWithPartialName” was mentioned, however that will load the DLL into memory, but doesn’t load them as modules for CmdLet use…

Chaining the two commands together does work nicely though:

$assembly = [System.Reflection.Assembly]::LoadWithPartialName(‘MyProject.PowerShell’)

Import-Module -Assembly $assembly

New-ObjectToPerformTask -Url $url

It’s nothing special, but a nice complete way to load PowerShell cmdlets using partial names from the GAC, so its great for SharePoint deployed DLLs.



SharePoint and Extension methods… super cool

I must admit that Extension methods in C# has got to be one of the coolest ideas ever for the language, for one huge reason.  They allow intelli-sense to automatically expose the methods as if they were part of the original class.  This opened up a huge opportunity for simplifying complex tasks into easily reusable bite that were automatically available once the containing assembly was referenced.  Now granted, this isn’t much different from writing custom library of methods to wrap all the heavy lifting, but extension methods put them right in front of you without needing to look them up, and that means people can’t help but use them… that’s cool.  This mean a more natural reuse of existing code, and that means more code usage which should help testing and code coverage.

Now, along comes SharePoint, a prime example of something hideously beautiful… even with all the new things added over the years its still at its heart a big customizable list manager, which lets you granularly control and render the types and views of the data in each list.  Unfortunately, like anything technology based… the simpler it is for the end user, the more complex it is for the engineers.  It’s like a self parking car… a $1 button on your dashboard probably equates to a life time of engineering and billions in R&D if you trace the evolution of all the tech involved.

SharePoint offers lots of control through a very extensive server side object model (there are also client side object models but that’s not the focus here), and everything is linked together in a nice parent child relationship of objects.  This is great for understanding the inner workings of everything, but day to day, and especially for code maintenance and robustness, its a bit of a pain.  Two of the biggest pain points were security changes (not uncommon to be a pain), and setting the data of a specific list item field (its simple to do, but just as simple in what it does).

Starting with the security activities; these were one of the most obvious to implement as an extension method since there are multiple securable objects in SharePoint.  With a couple overloads tagged as extensions, I took the logic of adding for example down from finding the user by login name, checking if an role association already existed, and if not, finding the role definitions and then the particular role definition by name, creating a role association and then adding it and updating the securable, and turned it into a single call on and SPWebs and SPLists that takes a login name and role names as strings.  This mean that even both long time and recently hired developers writing code to manipulate the security in SharePoint simply had to call spWeb.AddMemberWithRole(“someuser”, “somerole”)… it just showed up for everyone to use; far easier.  Because it was so easy to use without looking for the methods, people weren’t rewriting new version, we just used what appeared as method of SPWeb and SPList objects.  This included demo data imports and data migrations, which meant the same block of code was easily reused and easily tested everywhere under tons of edge cases.

So I realize that by passing in two strings, means that we are not able to reuse references to underlying objects that we have already found when previously calling this method, and this is true, but given that where we used these, adding one user at a time in a stateless web environment, we usually started with string data for each request anyway.  We also could string together the logic of the larger extension method into smaller extension methods on each object, with things like FindOrCreateRoleAssociation, and such, covering all our needs but so far the need hasn’t come up and its been over three years.

Now, for the most powerful extension method in the arsenal, setting the field values on items.  This extension method is probably the most used and there is a reason for it.  Out of the box, SharePoint provides a simple indexed method for setting a field value in a list item, and it works ‘fine’ for most field types… the problem is that as simple as it is, it behaves just as simple.  It doesn’t do any thinking for us, which means you need to tell it exactly what to do.  It works fine for string and number typed fields, but once you start to deal with lookups and taxonomy fields, it requires a lot of help.  I am not going to go into specifics due to confidentiality, but essentially, this easy to access extension method provides two things that SharePoint doesn’t.

First, we would pass in an object type and try to figure out how it fits based on the field type we are setting.  For example, if you enter a “123;#Hello World” for a lookup field, or a SPFieldUserValue for a user field, we would let SharePoint handle it, but if you just entered “Hello World” it could use the information available with that Field type to figure out exactly what SharePoint needs for a fully qualified value.  By providing support for Lookups, Users, DateTime (with safe range checking), and Taxonomy fields (even supporting navigating term store paths), we were able to use this method for copying data in all our event receivers, custom input screens, and all of our data migration/importing (which means that we can provide highly adaptive importing reducing migration efforts).  This means that the same consistent data type handling use used everywhere, and after a lot of edge case handling, is far smarter and adaptive than SharePoint out of the box.

The second thing it does that SharePoint doesn’t do, is provide feedback about whether it actually preformed a change.  The method, tells us if it actually made a change, so that we can track our ‘sets’ and then only perform a SPItem.Update if we actually made a change.  Why is this important? Well, even though SharePoint has the raw data, it doesn’t detect if changes actually occurred, and that means that event receivers will always fire even if no changes occurred and AfterProperties are always set for any fields touched.  By tracking field changes ourselves and only saving when required, we are able to reduce the execution of event receivers to a minimum improving performance on saves.

As usual, none of these methods themselves are special, but the use of them as extension methods with a descriptive method name means that anyone working on the code can and will use it, improving custom code reuse, and reducing the number of replicated methods and helping new developer training.  Some of the hundreds of extension methods we use, like those couple mentioned becomes so natural to call that when working on something new performing doing basic SharePoint tasks you start typing the method names out of habit, forgetting that they aren’t yet there out of the box.

Refreshing SPWeb object during enumeration

This arose for me during a PowerShell script, when I had to enumerate each web, add a field to the content types used by a particular SharePoint List in each web, and then query the list items to set the values for that newly added column.

Updating the content types (including child types) was fine, however since I had already accessed the List’s content types to find the root types, the changes made weren’t reflected in memory within the List object. Attempts to update the list items for the newly added field failed with an error that they don’t exist or may have been deleted, even if I queried the new field specifically.

Getting the List again didn’t seem to help, and calling Update on the List threw a save conflict (possibly because the List’s instance of the content types had just been updated by the hierarchical save from the parent content type).

I didn’t want to just reopen the web since I was enumerating them and that would have required alot of messy code to track where I was and use more memory doubling up the references to the web (every little bit matters).

Unfortunately SharePoint doesn’t provide a way to “refresh” the in memory objects, I guess since they usually have very short life spans.

It does however provide a Close method, but no open method. Well after a bit of decompiling I found that there are a handful of properties that will trigger the same internal initialization as opening the web the first time. I decided to try the one with the smallest footprint, Exists.

So with the code (PowerShell, but would be same in C#, etc):

$exists = $spWeb.Exists

I was able to make some heavy changes, then Close and reopen the web (via Exists), and run some queries and updates, all without mucking up the web enumeration (for each loop in this case).

Essentially, a SPWeb re-open procedure maintaining the same SPWeb object referenced in memory.