Making use of transactions in Dynamics 365 Customer Engagement

I believe that if you have ever written a CRM plugin, you are aware of the event execution pipeline (https://msdn.microsoft.com/en-us/library/gg327941.aspx) and that the operation is run in transaction which means that if there will be any exception, the whole transaction will be rolled back. Pre-operation plugins and Post-Operation plugins are also run in transaction, so if there will be an exception raised by the plugin, changes will not be reflected in CRM. This includes not only chaning attributes for the entity that the plugin is running on – create/update/delete changes on any other entities are also rolled back. This is really convenient – we can perform a bunch of operations and we are sure that even if anything goes wrong during Post-Operation, everything will be changed back to the original state.

The usage of transactions can be embraced even more by using custom Actions and ExecuteTransactionRequest. Custom  Actions can also be run with a rollback option (which can be enabled or disabled on Action configuration page). ExecuteTransactionRequest allows to group different OrganizationRequests and send them in bulk to the server – they will be run in single transaction.

Ok, but how this transactional behaviour works in real world? To make it easier to understand for you I created a custom entity “new_lock” and prepared a very simple CRM plugin:

public void Execute(IServiceProvider serviceProvider)
{
    var factory = (IOrganizationServiceFactory)serviceProvider.GetService(typeof(IOrganizationServiceFactory));
    var service = factory.CreateOrganizationService(null);
    var @lock = new Entity("new_lock");
    @lock.Id = new Guid("590424F1-611F-E711-80D2-00155D010402");
    @lock["new_name"] = "lockme";
    service.Update(@lock);
    Thread.Sleep(30 * 1000);
}

I registered this plugin on Create message of the Contact entity. As you can see it simply retrieves the “new_lock” record and updates its name to some different value and then waits 30 seconds. Let’s open this record in a browser:

Now, let’s create a Contact (using a different browser window). After clicking “Save” you will notice that the loader starts but the data is not getting saved. That’s ok because our plugin is running in the background and it takes about 30 seconds to finish. If you try to save the opened “new_lock” record with some different name, you will notice that… you can’t do this:

This is the principal idea of transactions – by creating a Contact we opened a transaction and “locked” the “new_lock” record by updating it. Before the transaction is finished nothing can write to this record. After 30 seconds, our contact is created and the “new_lock” is updated with the new value. Is this a value from the plugin or from what we have entered on the form? Well it’s the second option, because we updated the value after the transaction has done it (it does not matter that it waited 30 seconds after that).

How can we make use of that transactional behaviour of CRM? I believe that a very cool feature that we can develop is proper auto-numbering. It’s pretty well known problem which is usually handled by some custom counter entity. The algorithm usually works like that:

  1. Run plugin on create of numbered entity
  2. Retrieve Counter
  3. Assign current value of counter to entity record
  4. Update counter with the next value
  5. Plugin ends

If you don’t have many users or some custom apps creating entities, you will probably never run into any concurrency problems. But imagine what will happen if you have two concurrent calls and both retrieved value of the counter before point 3 was fulfiled. This means that both records will have the same number and counter will be increased only by 1. Some may say – ok let’s use standard locking, we can have a static object to lock on and before plugin starts it’s core logic, the running thread must obtain the lock. That would work flawlessly on single-frontend-server environments. But what happens if there are more application servers for CRM? You cannot synchronize threads between different servers…

Knowing what we already know about transactions, we can easily modify this scenario to:

  1. Run plugin on create of numbered entity
  2. Retrieve Counter
  3. Update some dummy counter property to some dummy value (here we will lock the counter for usage only for this transaction)
  4. Retrieve Counter (now we are sure nobody will modify its value)
  5. Assign current value of counter to entity record
  6. Update counter with the next value
  7. Plugin ends (and any concurrent operations start from point 3)

This should work even on multi-server environments, because the transactions are locked on database level. Very simplified code (so pardon the style) can look like this:

public class TransactionPlugin : IPlugin
{
    public void Execute(IServiceProvider serviceProvider)
    {
        var context = (IPluginExecutionContext)serviceProvider.GetService(typeof(IPluginExecutionContext));
        var factory = (IOrganizationServiceFactory)serviceProvider.GetService(typeof(IOrganizationServiceFactory));
        var service = factory.CreateOrganizationService(null);

        var counter = GetCounter(service);
        counter["new_name"] = "lockme";
        service.Update(counter);

        //now counter is locked

        //we have to get it again to prevent race conditions
        counter = GetCounter(service);

        var target = (Entity)context.InputParameters["Target"];
        target["new_number"] = counter["new_nextnumber"];

        counter["new_nextnumber"] = (int)counter["new_nextnumber"] + 1;
        service.Update(counter);
        //after finishing the transaction, concurrent executes can go on from the lock
    }

    private Entity GetCounter(IOrganizationService service)
    {
        //return some counter
    }
}

Disable columns in editable grid

Editable grids are a long awaited feature of Dynamics 365. Without any fancy coding, they allow to provide users a nice and easy to use interface, for updating multiple records in an Excel-like experience. We can easily create a subgrid on the form, configure it to use an Editable grid as control and we are good to go, we can edit all the grid columns.

Przechwytywanie

But what if we would like to edit only some of the columns of the grid, not all of them? This is not configurable, either we have an editable grid with all the columns editable, or we don’t have editable grid at all. The only way of handling this with configuration is enabling Field Security Profile – if user will not have privilege to update the field, it will appear as disabled for him. Fortunately there are quite a few client SDK features, that will allow us to achieve our goal with a little bit of JavaScript. First, we should register a function for OnRecordSelect event on our grid:

Przechwytywanie

And my gridRowSelected function looks like that:

This function basically gets all attributes for the selected row and for specified attribute (in my case it was “odx_monthid”) disables the grid cell. Effects are the following:

Przechwytywanie

Great, so only Month column is currently not editable, but we can still edit Amount column. The only drawback of this solution is that this “lock” on the field is shown only when you click on the row (because we registered the function to be fired on OnRowSelect event). Couldn’t it be fired for OnLoad of the form? Unfortunately, according to MSDN documentation:

we cannot run this, when form loads, because the internals of the grid are not yet loaded. Still it is quite an acceptable workaround. Maybe in future releases, editable grid will receive some more features like configuration of disabled columns.

Using early bounds in plugin for multiple entities

Recently I was caught up in the discussion about early bound entities and late bound entities. One of the argument of the “late bound supporters” was the fact, that using late-bound allows reusing the same plugin for multiple entities (so for example create a plugin that runs for all activities or a common plugin for leads/opportunities/accounts). This argument is not valid, I will show you how to write a clean code, that uses modern approach for coding and is perfectly testable.

Let’s start with the late bound version of the plugin to give you an idea what are we trying to achieve here:

The plugin simply adds values of “new_netamount” and “new_margin” fields on the entity and sets field “new_totalsum” to a resulting value. Of course this can be simply achieved by using calculated field, but I just want to show the basic idea here, real world scenario is usually much more complicated.

If we register this field on pre-update of any entity containing field “new_totalsum”, “new_netamount” and “new_margin” it would basically do its job. If you are not an experienced CRM Developer, who remembers CRM 3.0 or 4.0, just an ordinary .NET Developer, you would probably say, that this code looks ugly. It’s almost like it was taken from some JavaScript library – where are all the types, what is the type of “new_totalsum”, which year is that, are we still in 2017? And yes, you’ll be right – this code simply looks awful, does not allow to use any of great refactoring tools, because it uses some “magic” dictionaries and keys and without access to CRM you would not even have a clue, what are the proper types of the properties. It’s exactly the same story as with ORM – who of us still uses plain ADO .NET and not, for example, Entity Framework? Such approach is much less error prone, testable and also much more friendly for CRM newbies. Code using early bounds may look like that:

Now it’s much better, but there is a significant problem with this code. We assumed that our plugin runs on Account entity. What if we will register it on Contact entity? Well, it will simply crash when we will try to convert our target!

So the basic approach would be to create a switch statement and simply check the entity type:

Ok so now we can register the plugin on multiple entities, but our code looks even worse than the first version, because we have a lot of code that is copy-pasted. Imagine that the operation would be much more complex and would change frequently in time – we would have to change all the switch statements every time.

To overcome this problem we will take advantage of the fact that all early-bound classes are partial, so they can implement any interface we want. Let’s create such interface and some helper partial classes:

It would be great if we could use this like that:

But unfortunately, our “Target” is an entity and we have to somehow convert it to an early bound. I developed a simple utility class that is capable of that:

Simple explanation of the code – during first execution of the plugin, all the early-bound types are cached in a dictionary, that can be later fast accessed from the code (in this case it’s InterfaceMocker). It simply instantiates the early-bound and copies all attributes inside. There is also an extension method that simplifies the usage for Entity. Now our plugin can simply look like that:

And that’s it! This code looks much better then late bound version, provides type-checking for entity attributes and also is very nice when we implement unit tests, as we have an interface to test, not a full early-bound. If our logic is more complex we can create some additional classes that will be dependent upon IEntityWithTotalSum interface, not Account or Opportunity entity.