ObjectDataSource to populate Report Parameters

[Ken]

My question is: Why does the report "get" the list of ProfileItems that it uses for the report parameter twice?
Here's the setup:

Q3 2015 report
Adding a ReportParameter (right click report surface, select ReportParameters...)
Click the Add button, name it ProfileId.
Open the AvailableValues drop down and add a new ObjectDataSource for the Data Source of this parameter.
I'm using simple "POCO" object that returns an IEnumerable<ProfileItem> and ProfileItem has a First/Last Name and an Id field. Using a quick SQL query it populates all the active profiles from the database. Simple so far. Set the ValueMember to the Id field (it's a Guid) and the DisplayMember to the name. All done! Oh wait...I also have to set the Value.
Also, the report doesn't like Guids, so I've added a getter property that just returns the Guid Id as string.
Ok, now it all works fine!

Except, I was nosey and noticed that it accesses the data source to return the list of ProfileItem twice.
Why would it access the function twice?

Thanks!

[Nasko]

Hello Ken,

The AvailableValues.DataSource will be called each time the report source is resolved by the Reporting engine. This will happen when you preview/run a report in a viewer, when your export/print a report, when you switch between print preview/interactive view.
This may also happen as many times as the Reporting engine requires the report source to be resolved. One of the purposes of the multiple calls is to correctly retrieve and display cascading parameters.

Regards,
Nasko
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