WPF Change ViewModel Property in View - wpf

Question

I have a WPF DataGrid with several Templated Columns containing Checkboxes.
If I press a specific Checkbox the source of another checkbox has to be set.
I have a Viewmodel with a Property called Property (yes i know :)), and this Property has the Property "Visible".
If I check the "Mandatory" checkbox I want the "Visible" Value to be set and so the visible Checkbox to be set too, but somehow this is not working.
Heres my code:
<toolkit:DataGridTemplateColumn Header="Mandatory" IsReadOnly="False">
<toolkit:DataGridTemplateColumn.CellTemplate>
<DataTemplate>
<StackPanel Orientation="Horizontal" HorizontalAlignment="Center">
<CheckBox IsChecked="{Binding Path=Mandatory,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}">
<CheckBox.Style>
<Style TargetType="{x:Type CheckBox}">
<Style.Triggers>
<DataTrigger Binding="{Binding Path=MandatoryDB}" Value="True">
<Setter Property="IsEnabled" Value="False" />
</DataTrigger>
<DataTrigger Binding="{Binding Path=MandatoryDB}" Value="False">
<Setter Property="IsEnabled" Value="True" />
</DataTrigger>
</Style.Triggers>
</Style>
</CheckBox.Style>
<i:Interaction.Triggers>
<i:EventTrigger EventName="Checked">
<ei:ChangePropertyAction TargetObject="{Binding UpdateSourceTrigger=PropertyChanged}" PropertyName="ReadOnly" Value="False" />
<ei:ChangePropertyAction TargetObject="{Binding NotifyOnSourceUpdated=True, UpdateSourceTrigger=PropertyChanged}" PropertyName="Visible" Value="True" />
</i:EventTrigger>
</i:Interaction.Triggers>
</CheckBox>
</StackPanel>
</DataTemplate>
</toolkit:DataGridTemplateColumn.CellTemplate>
</toolkit:DataGridTemplateColumn>
Thanks,
Jonny

Answer 1

I think what you're trying to do is to drive your business logic by your View which is a horrible anti-pattern. What you need to is when the value of the "Mandatory" checkbox is changed then your viewmodel needs to set other properties accordingly and alert your view that there was a change (INotifyPropertyChanged).
Your view should not set any viewmodel properties, it should only read them and pass user input, the only other things which your view needs to controll are converters and other view-only items.
Hope this helps

Answer 2

see if this can help you.
lets assume that you want to show yes, no and ans in your Datagrid. for this find the sample code below.
<DataGrid AutoGenerateColumns="False" ItemsSource="{Binding Coll}">
<DataGrid.Columns>
<DataGridTemplateColumn Header="Yes">
<DataGridTemplateColumn.CellTemplate>
<DataTemplate>
<CheckBox Width="50"
Height="50"
IsChecked="{Binding Yes,
Mode=TwoWay,
UpdateSourceTrigger=PropertyChanged}" />
</DataTemplate>
</DataGridTemplateColumn.CellTemplate>
</DataGridTemplateColumn>
<DataGridTemplateColumn Header="No">
<DataGridTemplateColumn.CellTemplate>
<DataTemplate>
<CheckBox Width="50"
Height="50"
IsChecked="{Binding No,
Mode=TwoWay,
UpdateSourceTrigger=PropertyChanged}" />
</DataTemplate>
</DataGridTemplateColumn.CellTemplate>
</DataGridTemplateColumn>
<DataGridTemplateColumn Header="Ans">
<DataGridTemplateColumn.CellTemplate>
<DataTemplate>
<Rectangle Width="100"
Height="50"
RadiusX="25"
RadiusY="25">
<Rectangle.Style>
<Style TargetType="{x:Type Rectangle}">
<Style.Triggers>
<DataTrigger Binding="{Binding Ans}" Value="true">
<Setter Property="Fill" Value="Green" />
</DataTrigger>
<DataTrigger Binding="{Binding Ans}" Value="false">
<Setter Property="Fill" Value="Red" />
</DataTrigger>
</Style.Triggers>
</Style>
</Rectangle.Style>
</Rectangle>
</DataTemplate>
</DataGridTemplateColumn.CellTemplate>
</DataGridTemplateColumn>
</DataGrid.Columns>
</DataGrid>
code behind
public partial class YesNoTest : Window
{
public YesNoTest()
{
InitializeComponent();
if (Coll == null)
{
Coll = new ObservableCollection<Anss>();
for (int index = 0; index < 10; index++)
{
Coll.Add(new Anss() { Yes = false, No = false, Ans = true });
}
}
this.DataContext = this;
}
private ObservableCollection<Anss> _coll;
public ObservableCollection<Anss> Coll
{
get { return _coll; }
set { _coll = value; }
}
}
public class Anss : INotifyPropertyChanged
{
private bool _Yes;
public bool Yes
{
get
{
return _Yes;
}
set { _Yes = value; OnChanged("Yes"); OnChanged("Ans"); }
}
private bool _No;
public bool No
{
get
{
if (_No == true)
Yes = false;
return _No;
}
set { _No = value; OnChanged("No"); OnChanged("Ans"); }
}
private bool _Ans;
public bool Ans
{
get
{
if (Yes == true)
_Ans = true;
else
_Ans = false;
return _Ans;
}
set { _Ans = value; OnChanged("Ans"); }
}
public event PropertyChangedEventHandler PropertyChanged;
public void OnChanged(string name)
{
if (PropertyChanged != null)
PropertyChanged(this, new PropertyChangedEventArgs(name));
}
}