Post date: Nov 11, 2014 4:41:25 AM
Normally we should not handle the text box textChanged event in code behind file if we committed to use MVVM pattern.
Here I have discussed how to handle this TextBox textChanged event in MVVM patter using relay command.
Simple way of doing this is:
<TextBox Text="{Binding ViewModelProperty, UpdateSourceTrigger=PropertyChanged}"></TextBox>
The Old way of doing this is mentioned below:
Define RealyCommand in model
public RelayCommand<String> OnSearchCommand { get; set; }
//initialize it
OnSearchCommand = new RelayCommand<string>(param => SearchSmartNotes(param));
//Method to call
private void SearchSmartNotes(String strText)
{
SearchText = strText;
//Do necessary things
}
In XAML just configure this relay command as I mentioned below
<TextBox BorderThickness="1" BorderBrush="Black"
Grid.Row="0" Grid.Column="0" Margin="10"
VerticalContentAlignment="Stretch" x:Name="SearchBox">
<interacitivy:Interaction.Triggers>
<interacitivy:EventTrigger EventName="TextChanged">
<interacitivy:InvokeCommandAction Command="{Binding OnSearchCommand}" CommandParameter="{Binding ElementName=SearchBox, Path=Text}">
</interacitivy:InvokeCommandAction>
</interacitivy:EventTrigger>
</interacitivy:Interaction.Triggers>
</TextBox>
/In case if you are not aware of how to create Relay command with parameter object, then just use below code
public class RelayCommand<T> : ICommand
{
private readonly Action<T> execute;
private readonly Predicate<T> canExecute;
public RelayCommand(Action<T> execute)
: this(execute, null)
{
}
public RelayCommand(Action<T> execute, Predicate<T> canExecute)
{
if (execute == null)
throw new ArgumentNullException("execute");
this.execute = execute;
this.canExecute = canExecute;
}
[DebuggerStepThrough]
public bool CanExecute(object parameter)
{
return canExecute == null || canExecute((T)parameter);
}
public void Execute(object parameter)
{
execute((T)parameter);
}
public void RaiseCanExecuteChanged()
{
if (CanExecuteChanged != null)
CanExecuteChanged(this, new EventArgs());
}
public event EventHandler CanExecuteChanged;
}