Commands:
In WPF
world, Commands are excuted on events triggered by mouse or keyboard.
They are a
loosely coupled way to bind the UI to the logic that performs the action.
Commands
give central Architecure for executing certain tasks from multiple actions
taken by User on UI across application.
for example
Application.Find command can be excuted upon click on menu or button if this
command are binded to that menu or button.
Principle
of implementing Command in WPF.
1.Command.It
can be ApplicationCommands for example
Find ,copy , paste or Custom commands derived from ICommand interface .
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Input;
namespace WPFCommands.Commands
{
public class AddCommand
{
static RoutedUICommand
_addcommands;
static
AddCommand()
{
InputGestureCollection
_gesturecol = new InputGestureCollection();
KeyGesture _key = new KeyGesture(Key.A, ModifierKeys.Control
);
MouseGesture _mouseclick = new MouseGesture(MouseAction.LeftClick);
_gesturecol.Add(_key);
_gesturecol.Add(_mouseclick);
_addcommands = new RoutedUICommand("Addcommands", "Addcommands", typeof(AddCommand),
_gesturecol);
}
public static RoutedUICommand
Addcommands
{
get { return _addcommands; }
2.CommandBinding:
To associate a command with source control and handler upon invoking of
command.
Add
namespace in Xaml where AddCommand has
been defined
<Window
xmlns:Local="clr-namespace:WPFCommands.Commands">
<Window.CommandBindings>
Add
CommandBindings
<CommandBinding Command="Local:AddCommand.Addcommands" Executed="_bindings_Executed" >
</CommandBinding>
</Window.CommandBindings>
3.Command
source: UI elements for example Button,menu item etc or gesture for example
Mouse click or pressing keyboard keys
defined in InputGestureCollection.
<StackPanel
Background="Aquamarine" HorizontalAlignment="Left" Height="158" Margin="125,105,0,0"
VerticalAlignment="Top" Width="358"
OpacityMask="{DynamicResource {x:Static
SystemColors.HighlightTextBrushKey}}">
<TextBlock
Background="White" TextWrapping="Wrap" Text="TextBlock" Height="37" Width="358"/>
<Button Height="50px"
Background="BlanchedAlmond" Command="Local:AddCommand.Addcommands" Content="Add" />
</StackPanel>
4.Command
Handler: a CommandHandler is method and it is excuted when command is invoked.
public partial class MainWindow : Window
{
...
void
_bindings_Executed(object sender, ExecutedRoutedEventArgs e)
{
MessageBox.Show("Hello");
}
}
This is a much simple example of using command but power of command come in use when UI code/presentation logic is placed into another class called ViewModal, a MVVM pattern. having Modal and UI logic handling UI events and properties.
