How to properly use radiobutton checked event in mvvm pattern? - wpf

Question

When a particular radiobutton is checked/clicked on I want to write some specific text for each of those radiobuttons in a particular textblock. How do I do that following the MVVM pattern ?
In my main viewmodel I have the following code...
public ICommand MyCommand { get; set; }
private string _txt;
public string Txt
{
get
{
return _txt;
}
set
{
_txt = value;
OnPropertyChanged("Txt");
}
}
private bool canexecutemethod(object parameter)
{
if (parameter != null)
{
return true;
}
else
{
return false;
}
}
private void executemethod(object parameter)
{
//what to do here;
}
public MainViewModel()
{
MyCommand = new RelayCommand(executemethod);
}
Also in the xaml:
<RadioButton VerticalAlignment="Center" Margin="15" Content="Name" Command="{Binding MyCommand}"/>
<RadioButton VerticalAlignment="Center" Margin="15" Content="Age" Command="{Binding MyCommand}"/>
<RadioButton VerticalAlignment="Center" Margin="15" Content="DOB" Command="{Binding MyCommand}"/>
<TextBlock Margin="5" Height="30" Width="150" Foreground="Red" Text="{Binding Txt, Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}"/>
Say when the first radiobutton is checked the textblock text should show some text like
Please enter a name
, when the second radiobutton is checked the textblock text should show some text like
Please enter a valid age/integer value
and so on...

Answer 1

it can be done without view model participation:
<RadioButton VerticalAlignment="Center" Margin="15" Content="Name" Name="chkName"/>
<RadioButton VerticalAlignment="Center" Margin="15" Content="Age" Name="chkAge"/>
<RadioButton VerticalAlignment="Center" Margin="15" Content="DOB" Name="chkDob"/>
<TextBlock Margin="5" Height="30" Width="150" Foreground="Red">
<TextBlock.Style>
<Style TargetType="TextBlock">
<Style.Triggers>
<DataTrigger Binding="{Binding ElementName=chkName,Path=IsChecked}" Value="True">
<Setter Property="Text" Value="Please enter a name"/>
</DataTrigger>
<DataTrigger Binding="{Binding ElementName=chkAge,Path=IsChecked}" Value="True">
<Setter Property="Text" Value="Please enter a valid age/integer value"/>
</DataTrigger>
</Style.Triggers>
</Style>
</TextBlock.Style>
</TextBlock>