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QuestionStyle.TargetType = Interface || abstract class Pin
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QuestionMVVM: Transfering data from ViewModel to Model, when and how ? [modified] Pin
Jean-Louis Leroy19-Jul-11 1:38
Jean-Louis Leroy19-Jul-11 1:38 
Hello,

There's a lot of talk on the net about the View-ViewModel interaction but little about the ViewModel-Model interaction.

I have a Report that has (as a composition) a collection of Parameters. So I have a ReportViewModel that has a collection of ParameterViewModels, a ReportView bound to the ReportViewModel, and the ReportView in turn carries an ItemsControl-full of UserControls bound to the ParameterViewModels. The ReportViewModel's constructor gets passed the Report object and passes the Parameter objects in turn to the sub-viewmodels.

The Views and ViewModels interact nicely, the ViewModels "load" themselves from the underlying Models. More precisely, they keep a reference to the Model and synthesize whatever information the View needs.

Now for what puzzles me: when/how does the data flow back from ViewModel to Model ? When/how does the user's gesturing finally impacts the Model ?

I see that there are at least two possibilities...

1/ Live-update the Model whenever the ViewModel changes. Whenever we want to run operations on the updated Report, there's nothing extra to do.

2/ Implement an explicit "Apply" method in both ViewModels - obviosuly ReportViewModel.Apply will call ParameterViewModel.Apply. Whenever we need an up-to-date Report, first call Apply then save it somewhere, or print it, whatever.

What's your take on this ?

Jean-Louis
modified on Tuesday, July 19, 2011 7:49 AM

AnswerRe: MVVM: Transfering data from ViewModel to View, when and how ? Pin
Pete O'Hanlon19-Jul-11 1:45
mvePete O'Hanlon19-Jul-11 1:45 
AnswerRe: MVVM: Transfering data from ViewModel to Model, when and how ? Pin
Abhinav S20-Jul-11 0:42
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GeneralRe: MVVM: Transfering data from ViewModel to Model, when and how ? Pin
Jean-Louis Leroy20-Jul-11 0:51
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GeneralRe: MVVM: Transfering data from ViewModel to Model, when and how ? Pin
SledgeHammer0120-Jul-11 6:36
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GeneralRe: MVVM: Transfering data from ViewModel to Model, when and how ? Pin
Jean-Louis Leroy20-Jul-11 8:22
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GeneralRe: MVVM: Transfering data from ViewModel to Model, when and how ? Pin
SledgeHammer0120-Jul-11 8:43
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GeneralRe: MVVM: Transfering data from ViewModel to Model, when and how ? [modified] Pin
Jean-Louis Leroy21-Jul-11 23:01
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GeneralRe: MVVM: Transfering data from ViewModel to Model, when and how ? Pin
Jean-Louis Leroy21-Jul-11 23:20
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GeneralRe: MVVM: Transfering data from ViewModel to Model, when and how ? Pin
Pete O'Hanlon21-Jul-11 23:29
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GeneralRe: MVVM: Transfering data from ViewModel to Model, when and how ? Pin
Jean-Louis Leroy21-Jul-11 23:51
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GeneralRe: MVVM: Transfering data from ViewModel to Model, when and how ? Pin
Pete O'Hanlon22-Jul-11 0:02
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GeneralRe: MVVM: Transfering data from ViewModel to Model, when and how ? Pin
SledgeHammer0122-Jul-11 6:39
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GeneralRe: MVVM: Transfering data from ViewModel to Model, when and how ? Pin
Sacha Barber22-Jul-11 11:27
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GeneralRe: MVVM: Transfering data from ViewModel to Model, when and how ? Pin
SledgeHammer0122-Jul-11 6:28
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GeneralRe: MVVM: Transfering data from ViewModel to Model, when and how ? Pin
Pete O'Hanlon21-Jul-11 23:27
mvePete O'Hanlon21-Jul-11 23:27 
GeneralRe: MVVM: Transfering data from ViewModel to Model, when and how ? Pin
SledgeHammer0122-Jul-11 6:45
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GeneralRe: MVVM: Transfering data from ViewModel to Model, when and how ? Pin
Pete O'Hanlon22-Jul-11 9:59
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