This question already has an answer here:
Binding to properties in both the ViewModel and CodeBehind
(1个答案)
在8个月前关闭。
单击 View 中的按钮时,我想传递ViewModel参数(类变量)。当指定一个字符串时,一切都变为现实,但是我需要从View类(函数 AddNewField )传递一个非字符串值。
Main.xaml :
更新。
我更改了代码,现在可以正常工作了
感谢 @ mm8
(1个答案)
在8个月前关闭。
单击 View 中的按钮时,我想传递ViewModel参数(类变量)。当指定一个字符串时,一切都变为现实,但是我需要从View类(函数 AddNewField )传递一个非字符串值。
Main.xaml :
...
<Button
x:Name="ButtonAddingField"
CommandParameter="{Binding Path=Myprop}"
Command="{Binding Path=Myprop, RelativeSource={RelativeSource AncestorType=UserControl}}" />
...
Main.cs :...
private Color myprop;
public Color Myprop
{
get => myprop;
}
...
this.DataContext = new FieldCollectionViewModel(fields); // fields - List<*my Model*>
...
FieldCollectionViewModel.cs :...
private DelegateCommand<object> addFieldCommand;
public ICommand AddFieldCommand {
get {
if (addFieldCommand == null) addFieldCommand = new DelegateCommand<object>(AddNewField);
return addFieldCommand;
}
}
private void AddNewField(object parameter)
{
// !!! parameter = ALWAYS NULL
}
...
和我的 DelegateCommand.cs: ...
public class DelegateCommand<T> : ICommand
{
#region Constructors
/// <summary>
/// Constructor
/// </summary>
public DelegateCommand(Action<T> executeMethod)
: this(executeMethod, null, false)
{
}
/// <summary>
/// Constructor
/// </summary>
public DelegateCommand(Action<T> executeMethod, Func<T, bool> canExecuteMethod)
: this(executeMethod, canExecuteMethod, false)
{
}
/// <summary>
/// Constructor
/// </summary>
public DelegateCommand(Action<T> executeMethod, Func<T, bool> canExecuteMethod, bool isAutomaticRequeryDisabled)
{
if (executeMethod == null) throw new ArgumentNullException("executeMethod");
_executeMethod = executeMethod;
_canExecuteMethod = canExecuteMethod;
_isAutomaticRequeryDisabled = isAutomaticRequeryDisabled;
}
#endregion Constructors
#region Public Methods
/// <summary>
/// Method to determine if the command can be executed
/// </summary>
public bool CanExecute(T parameter)
{
if (_canExecuteMethod != null) return _canExecuteMethod(parameter);
return true;
}
/// <summary>
/// Execution of the command
/// </summary>
public void Execute(T parameter)
{
if (_executeMethod != null) _executeMethod(parameter);
}
/// <summary>
/// Raises the CanExecuteChaged event
/// </summary>
public void RaiseCanExecuteChanged()
{
OnCanExecuteChanged();
}
/// <summary>
/// Protected virtual method to raise CanExecuteChanged event
/// </summary>
protected virtual void OnCanExecuteChanged()
{
CommandManagerHelper.CallWeakReferenceHandlers(_canExecuteChangedHandlers);
}
/// <summary>
/// Property to enable or disable CommandManager's automatic requery on this command
/// </summary>
public bool IsAutomaticRequeryDisabled {
get => _isAutomaticRequeryDisabled;
set {
if (_isAutomaticRequeryDisabled != value)
{
if (value)
CommandManagerHelper.RemoveHandlersFromRequerySuggested(_canExecuteChangedHandlers);
else
CommandManagerHelper.AddHandlersToRequerySuggested(_canExecuteChangedHandlers);
_isAutomaticRequeryDisabled = value;
}
}
}
#endregion Public Methods
#region ICommand Members
/// <summary>
/// ICommand.CanExecuteChanged implementation
/// </summary>
public event EventHandler CanExecuteChanged {
add {
if (!_isAutomaticRequeryDisabled) CommandManager.RequerySuggested += value;
CommandManagerHelper.AddWeakReferenceHandler(ref _canExecuteChangedHandlers, value, 2);
}
remove {
if (!_isAutomaticRequeryDisabled) CommandManager.RequerySuggested -= value;
CommandManagerHelper.RemoveWeakReferenceHandler(_canExecuteChangedHandlers, value);
}
}
bool ICommand.CanExecute(object parameter)
{
// if T is of value type and the parameter is not
// set yet, then return false if CanExecute delegate
// exists, else return true
if (parameter == null &&
typeof(T).IsValueType)
return _canExecuteMethod == null;
return CanExecute((T)parameter);
}
void ICommand.Execute(object parameter)
{
Execute((T)parameter);
}
#endregion ICommand Members
#region Data
private readonly Action<T> _executeMethod;
private readonly Func<T, bool> _canExecuteMethod;
private bool _isAutomaticRequeryDisabled;
private List<WeakReference> _canExecuteChangedHandlers;
#endregion Data
}
...
我该如何解决我的问题?更新。
我更改了代码,现在可以正常工作了
感谢 @ mm8
最佳答案
Myprop
必须是DataContext
的Button
的公共(public)属性,以便您当前的绑定(bind)起作用。
如果它是父UserControl
的属性,则可以使用RelativeSource
绑定(bind)到它:
CommandParameter="{Binding Path=Myprop, RelativeSource={RelativeSource AncestorType=UserControl}}"
请注意,您只能绑定(bind)到公共(public)属性。您无法绑定(bind)到字段。关于c# - 在MVVM中使用CommandParameter传递类变量,我们在Stack Overflow上找到一个类似的问题:https://stackoverflow.com/questions/62537823/