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using System;
using System.Windows.Input;
namespace VersOne.Epub.WpfDemo.Utils
{
/// <summary>
/// A custom command which uses an action and an optional predicate supplied through one of its constructors.
/// The predicate is used to determine if the command can be executed and the action is called with the command is executed.
/// </summary>
public class Command : ICommand
{
private readonly Predicate<object> canExecute = null;
private readonly Action<object> executeAction = null;
/// <summary>
/// Initializes a new instance of the <see cref="Command" /> class with a specified execute action.
/// </summary>
/// <param name="executeAction">An action that needs to be executed when the <see cref="Execute" /> method is called.</param>
public Command(Action executeAction)
: this(param => true, param => executeAction())
{
}
/// <summary>
/// Initializes a new instance of the <see cref="Command" /> class with a specified execute action.
/// </summary>
/// <param name="executeAction">An action that needs to be executed when the <see cref="Execute" /> method is called.</param>
public Command(Action<object> executeAction)
: this(param => true, executeAction)
{
}
/// <summary>
/// Initializes a new instance of the <see cref="Command" /> class with a specified predicate that determines whether the action can be executed or not
/// and a specified execute action.
/// </summary>
/// <param name="canExecute">A predicate that is executed when the <see cref="CanExecute" /> method is called.</param>
/// <param name="executeAction">An action that needs to be executed when the <see cref="Execute" /> method is called.</param>
public Command(Predicate<object> canExecute, Action<object> executeAction)
{
this.canExecute = canExecute;
this.executeAction = executeAction;
}
/// <summary>
/// Occurs after the execution of the <see cref="Execute" /> method, so the consumer of this command can check whether the command can still be executed or not.
/// </summary>
public event EventHandler CanExecuteChanged;
/// <summary>
/// Determines whether the command can execute in its current state.
/// </summary>
/// <param name="parameter">
/// Data used by the predicate supplied through the constructor of this command.
/// If the predicate does not require data to be passed, this object can be set to <c>null</c>.
/// </param>
/// <returns><c>true</c> if this command can be executed; otherwise, <c>false</c>.</returns>
public bool CanExecute(object parameter)
{
if (canExecute != null)
{
return canExecute(parameter);
}
return true;
}
/// <summary>
/// Method called when the command is invoked.
/// </summary>
/// <param name="parameter">
/// Data used by the action supplied through the constructor of this command.
/// If the action does not require data to be passed, this object can be set to <c>null</c>.
/// </param>
public void Execute(object parameter)
{
executeAction?.Invoke(parameter);
UpdateCanExecuteState();
}
/// <summary>
/// Triggers the <see cref="CanExecuteChanged" /> event.
/// </summary>
public void UpdateCanExecuteState()
{
CanExecuteChanged?.Invoke(this, new EventArgs());
}
}
}
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