Update source trigger when a button is clicked? - mvvm

Question

i've a contentcontrol in my Wpf-App (MVVM) which is bound to an object and displays the objects properties in textboxes, so the user can edit the values of the properties.
i have to buttons in my control "Ok" and "Cancel".. I would like to use UpdateSourceTrigger="Explicit" so that the ViewModel only gets updated when the user explicitly clicks 'Ok', rather than updating as textbox values are modified. How do i achive this.
this is how my viewmodel looks like..
class NeedViewModel : CarePlanEntityViewModelBase
{
public CPLNursingNeedVersion CurrentNeedVersion
{
get { return currentNeedVersion; }
set
{
currentNeedVersion = value;
this.OnPropertyChanged("CurrentNeedVersion");
}
}
}
this is how my view looks like
<DataTemplate x:Key="NeedDataEntryDataTemplate">
<Border Background="White"
BorderThickness="2"
BorderBrush="#4682B4"
local:PublishReadOnlyProperty.Observe="True"
local:PublishReadOnlyProperty.ActualWidth="{Binding Path=Width,Mode=OneWayToSource,UpdateSourceTrigger=PropertyChanged}"
MinWidth="410">
<Grid Name="mainGrid">
<Grid.BindingGroup>
<BindingGroup>
</BindingGroup>
</Grid.BindingGroup>
<Grid.RowDefinitions>
<RowDefinition Height="28" MinHeight="28"/>
<RowDefinition Height="Auto"></RowDefinition>
<RowDefinition Height="Auto"></RowDefinition>
<RowDefinition Height="Auto"></RowDefinition>
<RowDefinition Height="Auto"></RowDefinition>
<RowDefinition Height="Auto"></RowDefinition>
<RowDefinition Height="Auto"></RowDefinition>
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="7" MaxWidth="7"></ColumnDefinition>
<ColumnDefinition Width="Auto"></ColumnDefinition>
<ColumnDefinition Width="Auto"></ColumnDefinition>
<ColumnDefinition Width="Auto"></ColumnDefinition>
<ColumnDefinition Width="*"></ColumnDefinition>
<ColumnDefinition Width="68" MaxWidth="75"></ColumnDefinition>
<ColumnDefinition Width="10" MaxWidth="10"></ColumnDefinition>
<ColumnDefinition Width="68" MaxWidth="75"></ColumnDefinition>
</Grid.ColumnDefinitions>
<Label Padding="0,3,0,3"
Name="label9"
Grid.Row="1" Grid.Column="1"
Margin="3"
FontSize="13"
HorizontalAlignment="Left" >Voimassaoloaika:</Label>
<hcw:HCWDateTimePicker Padding="0,3,0,3"
x:Name="startDateTimePicker"
Grid.Row="1" Grid.Column="2"
Margin="5,3,3,3"
FontSize="13"
HorizontalAlignment="Left"
MaxWidth="120"
DateControlMode="Mandatory"
SelectedDate="{Binding Path=CurrentNeedVersion.ValidFromDate,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}"
DisplayMode="DateOnly" />
<Label Padding="0,3,0,3"
Name="label8"
Grid.Row="1" Grid.Column="3"
Margin="3,3,3,3"
HorizontalAlignment="Center"
FontSize="13">-</Label>
<hcw:HCWDateTimePicker x:Name="endDateTimePicker"
Padding="0,3,0,3"
Grid.ColumnSpan="5" Grid.Row="1" Grid.Column="4"
Margin="3"
FontSize="13"
HorizontalAlignment="Left"
MaxWidth="120"
DisplayMode="DateOnly"
SelectedDate="{Binding Path=CurrentNeedVersion.ValidToDate,Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" />
<Label Name="label26"
Padding="0,3,0,3"
FontSize="13"
Grid.Row="2" Grid.Column="2"
Margin ="20,3,3,3"
HorizontalAlignment="Left"
Grid.ColumnSpan="6">Huomiomerkitty</Label>
<CheckBox Padding="0,3,0,10"
Grid.Row="2" Grid.Column="2"
IsChecked="{Binding Path=CurrentNeedVersion.IsNoteworthy,Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"
Name="note"
FontSize="13"
Margin="3,3,20,3"
VerticalAlignment="Center"
HorizontalAlignment="Left"
IsEnabled="True" />
<ContentControl Content="{Binding}"
Grid.Row="3" Grid.ColumnSpan="9"
ContentTemplate="{DynamicResource ClassificationSelectorDataTemplate}"/>
<Label Padding="0,3,0,3"
Grid.Row="4" Grid.Column="1"
Margin="3"
FontSize="13"
Name="needLabel"
HorizontalAlignment="Left" >Tarve:</Label>
<hcw:HCWTextBox Padding="3,3,0,3"
Grid.Row="4" Grid.Column="2" Grid.ColumnSpan="6"
FontSize="13"
Margin="3"
Name="needTextBox"
Text="{Binding Path=CurrentNeedVersion.NeedText, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"
TextWrapping="Wrap"
AcceptsReturn="True" />
<Label Padding="0,3,0,3"
Margin="3"
Name="goalLabel"
FontSize="13"
Grid.Row="8" Grid.Column="1" Grid.ColumnSpan="1">Tavoite:</Label>
<TextBox Padding="0,3,0,3"
Grid.Row="8" GridColumn="2" Grid.ColumnSpan="6"
FontSize="13"
Margin="3"
Text="{Binding Path=CurrentNeedVersion.GoalText, Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}"
HorizontalAlignment="Stretch"
Name="goalTextBox"
TextWrapping="Wrap"
AcceptsReturn="True" />
<Label Name="temporaryLabel"
Padding="0,3,0,3"
FontSize="13"
Grid.Row="9" Grid.Column="2" Grid.ColumnSpan="6"
Margin="20,3,3,3"
HorizontalAlignment="Left">Keskeneräinen</Label>
<CheckBox Padding="0,3,0,10"
Grid.Row="9" Grid.Column="2"
Name="temporaryCheckBox"
FontSize="13"
Margin="3,3,20,3"
VerticalAlignment="Center"
HorizontalAlignment="Left"
IsEnabled="True" />
<Button Name="acceptButton"
Command="{Binding Path=AcceptNeedDEC}"
Margin="0,0,0,7"
Grid.Row="10" Grid.Column="5"
FontSize="13"
MinWidth="68"
Content="OK"
VerticalAlignment="Center"
Background="WhiteSmoke" />
<Button Command="{Binding Path=CloseDEC}"
Name="cancelButton"
Margin="0,0,0,7"
Grid.Row="10" Grid.Column="7"
HorizontalAlignment="Right"
FontSize="13"
MinWidth="68"
Content="Peruuta"
VerticalAlignment="Center"
Background="WhiteSmoke" />
</Grid>
</Border>
</DataTemplate>

Answer 1

You need to do it in code-behind:
var bindingExpression = BindingOperations.GetBindingExpression(startDateTimePicker, HCWDateTimePicker.SelectedDateProperty);
bindingExpression.UpdateSource();

Answer 2

You could take all of the properties the View is binding to and place them in a different class. Then have two instances of that class in the ViewModel, one public for data binding, and a private one. Once the button is clicked, copy the values from the public one to the private one, then run all of your logic against the private one.