Power Platform Community Forum Thread Details

Collections, Dataverse columns...help please

Hi all,

I've started following a Youtube Video on drop and drag as a little project, I was doing relatively ok but I'm really struggling getting my head around what needs to be in a column in my dataverse table and what some of the actions in the video mean and are trying to achieve.

Such as As Contact, what is this and what's it trying to do, should it be in a column in my table or is it creating a column in my collection? Also Entity image, should this be a column? Same question on First Name and Last name, I'm a little confused and can't work out what certain things are for and should they be pulling in from a column, any help would be appreciated. Also is there any such thing as a Power App mentor? I enjoy the little apps I have made and would love to understand it all more. Thanks in advance

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Power Apps component framework

Application Lifecycle Management (ALM)

Power Platform Build Tools

Hi @jsmith87

I'd have to see exactly what the video is and understand all you are doing

The As function expression works in multiple ways depending on its use

Use as a Cast

In your case, you are using FirstN( to return back a number of records in your datasource Engineers.

As allows you to Cast the existing object, into a specific Type, in this case it takes the Object type and turns it into a Contact object, so that all properties that exist on Contact are available to you via .Notation. This assumes that the Object is actually castable as another Type. This is not the same as a reference, as it's Casting it to something else.

This usage is done often, when you look at the Customer object in Dataverse or Owner. These can be cast as Either a Contact as an Account for instance. So the object you want to cast, will be one or the other, but you see the Column as Customer which is stored as a lookup that is EITHER a Contact or an Account. So you have to Cast it, if you want to get to the properties.

In your case then you can access things like Address, Name attributes etc. as if it was always a Contact.

Use as a Reference

To further help understand As, you can use it to reference something as an Alias.

As an example,

Lets say you are looping through a Collection.

You will have 1-M loop iterations depending on how many there are.

Image you had this Loop.

In every loop interation you access the current Data in the DataSource by using the syntax ThisRecord. , where ThisRecord is a pointer to the actual data for this iteration.

ForAll(MyCollectionA,
     Patch(MyDatasource, ColumnA: ThisRecord.Somedata
) ;

Now Let's say you have 2 collections

You want to loop through CollectionA, then Loop through CollectionB and then to do something.

It would look like the below.

BUT you have a big issue. You cannot use ThisRecord to access CollectionA Data because its not in scope, currently in the loops you are in scope of the second loop. So how to fix this.

With a Reference Alias

ForAll(CollectionA,
   ForAll(ColectionB, 
       Patch(MyDataSource,
           {
              ColumnA: ThisRecord.CollectionAData,
             ColumnB: ThisRecord:CollectionBData
            }   
     )
   )
)

So now we change it to something like this, so that the Platform knows exactly what you are trying to access.

Now the inner loop knows how to reference CollectionA data, so we instead create a reference to it, and called it DataA instead. Just like in SQL Server (if you use that)

ForAll(CollectionA As DataA,
   ForAll(ColectionB, 
       Patch(MyDataSource,
           {
              ColumnA: DataA.CollectionAData,
             ColumnB: ThisRecord:CollectionBData
            }   
     )
   )
)

Now let's talk about Entity Image

So in Dataverse (more specifically and originally with Dynamics 365 Customer Engagement), people needed a way to do the following:

Make a Change on a Row of data WITH THESE caveats. Now to understand these you need some more details.

In Dataverse, data goes through multiple stages before it actually gets saved for good

Some are Pre-stages, which allow you to do internal data checks and even roll it back if you don't like what the data is

Some as saving

Some post saving

An Entity Image, is a Snapshop of the Entity (Row as its now) within the table So let do this

Row in a Table that has a column shoe size with value 11

Create a SnapShot of the row

"Pre-assign" the new value to see if you like it

Change the value to 11, compare it with the Entity image if you like or business rule, go ewwww no, reject the change

Post assign.

oh wow, we made a mistake, we need to make sure after saving if its really want we want, because post saving could be no good, so you could roll it back after comparing to the image.

So images are snapshots of the Record, to be used in the Stages of saving data so you can verify if you even want to do it.

Also, you can use this to update the Picture a person has on their profile :-)

I hope that helps, it's the most teaching ;-) on this topic ever in a post lol.

If this helps you please Mark as such and maybe a like.

Cheers

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