Error when setting Model Property to a BusinessListBase

Error when setting Model Property to a BusinessListBase

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Jav posted on Friday, August 13, 2010

I have made a lot of progress with my ViewModel implementation.  For week I was using a single Root object based ViewModel.  I have now successfully created ViewModels for each object in the object graph, and have also trasferred most of my code-behind into the appropriate VMs.

Parts of my object graph are created/fetched at the outset, and parts will be lazy-loaded (and are not even implemented yet).  All child object VMs are created using a constructor that is sent the object as a parameter. 

Right now there is only one BusinessListBase collection, and that is giving me an error.  The error says "BeginEdit is not valid on a child object" and occures when VM's Model property is set to my List in the ViewModelBase.  I see in SlDemo the EmployeeListViewModel being created with the Parameterless constructor using BeginRefresh("GetEmployeeList"); 

The phrase BeginEdit does not even occur anywhere in my solution.  Is there something wrong with my List that is generating this error?

RockfordLhotka replied on Friday, August 13, 2010

ViewModelBase defaults to ManageObjectLifetime=true, which means it calls BeginEdit/CancelEdit/ApplyEdit on your behalf. You can set ManageObjectLifetime=false in your constructor to prevent this behavior, which is usually what you want to do for anything other than the root object - and you want to set it to false for a root object if your UI has no concept of a cancel button.

Jav replied on Friday, August 13, 2010

Fantastic.  Thank you.  That makes perfect sense.


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