WPF MVVM命令可以执行启用/禁用按钮 [英] WPF MVVM command canexecute enable/disable button
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问题描述
我想在文本框属性文本不为null时启用RibbonButton.当文本框属性文本为null时,禁用RibbonButton.我想在ICommand中使用CanExecute方法.我该怎么办?
I want to enable RibbonButton when textbox property text isn't null. Disable RibbonButton when textbox property text is null. I want to use CanExecute method in ICommand for it. How can I do it?
查看:
<Custom:RibbonButton
LargeImageSource="..\Shared\img\save_diskete.png"
Label="Save"
Command="{Binding ButtonCommand}">
</Custom:RibbonButton>
ViewModel
class KomentarViewModel:BaseViewModel
{
#region Data
private ICommand m_ButtonCommand;
public ICommand ButtonCommand
{
get
{
return m_ButtonCommand;
}
set
{
m_ButtonCommand = value;
}
}
private string textKomentar;
public string TextKomentar
{
get
{
return this.textKomentar;
}
set
{
// Implement with property changed handling for INotifyPropertyChanged
if (!string.Equals(this.textKomentar, value))
{
textKomentar = value;
OnPropertyChanged("TextKomentar");
}
}
}
private ObservableCollection<Komentar> allCommentsInc;
public ObservableCollection<Komentar> AllCommentsInc
{
get
{
return allCommentsInc;
}
set
{
allCommentsInc = value;
OnPropertyChanged("AllCommentsInc");
}
}
public int idIncident { get; private set; }
public Incident incident { get; private set; }
#endregion
#region Constructor
public KomentarViewModel(int id)
{
CC_RK2Entities context = new CC_RK2Entities();
this.idIncident = id;
AllCommentsInc = new ObservableCollection<Komentar>(context.Komentar.Where(a => a.Incident_id == idIncident));
incident = context.Incident.Where(a => a.id == idIncident).First();
//ButtonCommand = new RelayCommand(new Action<object>(ShowMessage));
}
#endregion
#region Methods
//ukaz napsany text
public void ShowMessage(object obj)
{
//MessageBox.Show(obj.ToString());
MessageBox.Show(this.TextKomentar);
}
}
RelayCommand
namespace Admin.Shared.Commands
{
class RelayCommand : ICommand
{
private Action<object> _action;
public RelayCommand(Action<object> action)
{
_action = action;
}
#region ICommand Members
public bool CanExecute(object parameter)
{
return true;
}
public event EventHandler CanExecuteChanged;
public void Execute(object parameter)
{
_action(parameter);
}
#endregion
}
}
推荐答案
您需要像这样修改RelayCommand类
You need to modify your RelayCommand class like this
class RelayCommand : ICommand
{
private Action<object> _action;
private Func<bool> _func;
public RelayCommand(Action<object> action,Func<bool> func)
{
_action = action;
_func = func;
}
public void RaiseCanExecuteChanged()
{
if(CanExecuteChanged!=null)
CanExecuteChanged(this,new EventArgs());
}
#region ICommand Members
public bool CanExecute(object parameter)
{
if (_func != null)
return _func();
return true;
}
public event EventHandler CanExecuteChanged;
public void Execute(object parameter)
{
_action(parameter);
}
#endregion
}
将ButtonCommand初始化为
Initialize ButtonCommand as
ButtonCommand = new RelayCommand((s) => ShowMessage(s),()=>!string.IsNullOrEmpty(TextKomentar));
RaiseCanExcuteChanged来自Text属性的设置器
RaiseCanExcuteChanged from the setter of Text property
public string TextKomentar
{
get
{
return this.textKomentar;
}
set
{
// Implement with property changed handling for INotifyPropertyChanged
if (!string.Equals(this.textKomentar, value))
{
textKomentar = value;
OnPropertyChanged("TextKomentar");
}
ButtonCommand.RaiseCanExecuteChanged();
}
}
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