Question

I have a class MyDataCollection that contains MyMetaData and MyData. In my application i have two usercontrolls that display input fields to the user. One for the MyMetaData and the other for MyData. Both usercontrols are included in the MainPage.

My Question is: How should i get the data from the usercontrols then the user klicks on the save-button (located on the mainpage)?

Update
I have changed my code accordingly to blindmeis post but now the MetaDataView is not shown:

<UserControl.Resources>
    <DataTemplate x:Key="MetaDataTemplate">
        <view:MetaDataView/>
    </DataTemplate>
</UserControl.Resources>

<Grid>
    <ContentPresenter Content="{Binding MetaDataTemplate}"/>
</Grid>

Answer 1

why not doing mvvm the easy way?(viewmodel first). you say you have a mainpage – this means you also have a mainpageviewmodel. your mainpageviewmodel handles at least the save command. now you want to show MyMetaData and MyData on your mainpage. so the easy way would be to create one MyMetaData instance and one MyData instance in your mainviewmodel.

public class MainPageViewmodel
{
    public ICommand SaveCommand { get; set; }
    public MyDataViewmodel MyData { get; set; }
    public MyMetaDataViewmodel MyMetaData { get; set; }

    public MainPageViewmodel()
    {
        this.MyData = new MyDataViewmodel();
        this.MyMetaData = new MyMetaDataViewmodel();
    }

}

public class MyDataViewmodel
{}

public class MyMetaDataViewmodel
{}

your mainpage just need 2 datatemplates and 2 contentpresenter.

//resources

    <DataTemplate DataType="{x:Type Local:MyDataViewmodel}">
        <view:MyDataUserControl/>
    </DataTemplate>
    <DataTemplate DataType="{x:Type Local:MyMetaDataViewmodel}">
        <view:MyMetaDataUserControl/>
    </DataTemplate>

<Grid>
    <Grid.ColumnDefinitions>
        <ColumnDefinition/>
        <ColumnDefinition/>
        <ColumnDefinition/>
    </Grid.ColumnDefinitions>
    <ContentPresenter Content="{Binding MyData}" Grid.Column="0"/>
    <ContentPresenter Content="{Binding MyMetaData}" Grid.Column="1"/>
    <Button Content="Save" Command="{Binding SaveCommand}" Grid.Column="2"/>
</Grid>

because your mainpageviewmodel has both “child” viewmodel, you have all information you want on your savecommand.

if you have another scenario pls update your question, maybe post some code.

EDIT: i have no silverlight so that just a suggestion: maybe rachel can give you a better answer.

<Grid>
  <ContentPresenter Content="{Binding MyMetaData}" ContentTemplate="{StaticResource MetaDataTemplate}"/>
</Grid>

if silverlight cant handle datatemplates with datatype you could just put the usercontrol there directly.

<Grid>
    <Grid.ColumnDefinitions>
        <ColumnDefinition/>
        <ColumnDefinition/>
        <ColumnDefinition/>
    </Grid.ColumnDefinitions>
    <view:MyDataUserControl DataContext="{Binding MyData}" Grid.Column="0"/>
    <view:MyMetaDataUserControl DataContext="{Binding MyMetaData}" Grid.Column="1"/>
    <Button Content="Save" Command="{Binding SaveCommand}" Grid.Column="2"/>
</Grid>