سلام.
به نظر من command ها به درد MVVM میخورن....
شما رویداد ها رو میتونید به صورت command به کنترل بایند کنید.
مثلاً میخواهید در زمان بخصوصی enable کنترل شما فعال باشه .
برای مثال command کنترل button همون رویداد کلیک میتونه باشه....
این دو کلاس RelayCommand برای استفاده از Command ها:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows.Input;
using System.Diagnostics;
namespace Copy_My_Files.Businesses
{
// Summary:
// A generic command whose sole purpose is to relay its functionality to other
// objects by invoking delegates. The default return value for the CanExecute
// method is 'true'. This class allows you to accept command parameters in the
// Execute and CanExecute callback methods.
//
// Type parameters:
// T:
// The type of the command parameter.
[Serializable]
public class RelayCommand<T> : ICommand
{
#region Fields
readonly Action<T> _execute = null;
readonly Predicate<T> _canExecute = null;
#endregion // Fields
#region Constructors
public RelayCommand(Action<T> execute)
: this(execute, null)
{
}
/// <summary>
/// Creates a new command.
/// </summary>
/// <param name="execute">The execution logic.</param>
/// <param name="canExecute">The execution status logic.</param>
public RelayCommand(Action<T> execute, Predicate<T> canExecute)
{
if (execute == null)
throw new ArgumentNullException("execute");
_execute = execute;
_canExecute = canExecute;
}
#endregion // Constructors
#region ICommand Members
[DebuggerStepThrough]
public bool CanExecute(object parameter)
{
return _canExecute == null ? true : _canExecute((T)parameter);
}
public event EventHandler CanExecuteChanged
{
add { CommandManager.RequerySuggested += value; }
remove { CommandManager.RequerySuggested -= value; }
}
public void Execute(object parameter)
{
_execute((T)parameter);
}
#endregion // ICommand Members
}
public class RelayCommand : ICommand
{
#region Fields
readonly Action _execute = null;
readonly Func<bool> _canExecute = null;
#endregion // Fields
#region Constructors
public RelayCommand(Action execute)
: this(execute, null)
{
}
/// <summary>
/// Creates a new command.
/// </summary>
/// <param name="execute">The execution logic.</param>
/// <param name="canExecute">The execution status logic.</param>
public RelayCommand(Action execute, Func<bool> canExecute)
{
if (execute == null)
throw new ArgumentNullException("execute");
_execute = execute;
_canExecute = canExecute;
}
#endregion // Constructors
#region ICommand Members
[DebuggerStepThrough]
public bool CanExecute(object parameter)
{
return _canExecute == null ? true : _canExecute();
}
public event EventHandler CanExecuteChanged
{
add { CommandManager.RequerySuggested += value; }
remove { CommandManager.RequerySuggested -= value; }
}
public void Execute(object parameter = null)
{
_execute();
}
#endregion // ICommand Members
}
}
بعنوان مثال کد زیر در کلاسی قرار داده میشود که قرار است بایند شود:
public RelayCommand SelectFolderCommand
{
get;
private set;
}
کد xaml:
<Button Command="{Binding SelectFolderCommand}" Content="Select Folder" Height="23" HorizontalAlignment="Left" Margin="12,12,0,0" VerticalAlignment="Top" Width="103" />
و در انتها مثالی برای اجرای کامند:
SelectFolderCommand = new RelayCommand(() =>
{
//زمانی که کامند اجرا شد
},
() =>
{
//false برای غیر فعال کردن کامند مقدار
//true برای فعال کردن کامند مقدار
return false;
});
موفق و سربلند باشید.