Question

很抱歉，如果这是一个愚蠢的问题，但我似乎无法解决，基本上我在窗口上有一个按钮来保存数据。我在这里提到了一类RelayCommand（最佳答案） Binding Button click to a method 每次运行我的项目时，都会触发ICommand SaveCommand方法。从这里创建了一个循环并不断循环。但是，当窗口出现时，按“保存”按钮实际上不会导致命中ICommand SaveCommand方法。我该如何解决这个问题？谢谢大家。

我的观点：

<av:Button x:Name="btnSave" Content="Save" HorizontalAlignment="Left" VerticalAlignment="Bottom" Width="81" Height="44" Margin="52,0,0,20" av:Grid.RowSpan="2" Command ="{Binding SaveCommand}"/>

我的ViewModel：

private void OnPropertyChanged(string propertyName)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
        }
    }

    private ICommand _saveCommand;

    public ICommand SaveCommand
    {
        get
        {
            if (_saveCommand == null)
            {
                _saveCommand = new RelayCommand(
                    param => this.SaveObject(),
                    param => this.CanSave()
                    );
            }
            return _saveCommand;
        }
    }

    private bool CanSave()
    {
        // Verify command can be executed here

        return true;
    }

    private void SaveObject()
    {
        // Save command execution logic
    }

RelayCommand Class：

public class RelayCommand : ICommand
{
    #region Fields

    readonly Action<object> _execute;
    readonly Predicate<object> _canExecute;

    #endregion // Fields

    #region Constructors

    /// <summary>
    /// Creates a new command that can always execute.
    /// </summary>
    /// <param name="execute">The execution logic.</param>
    public RelayCommand(Action<object> 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<object> execute, Predicate<object> canExecute)
    {
        if (execute == null)
            throw new ArgumentNullException("execute");

        _execute = execute;
        _canExecute = canExecute;
    }

    #endregion // Constructors

    #region ICommand Members

    [DebuggerStepThrough]
    public bool CanExecute(object parameters)
    {
        return _canExecute == null ? true : _canExecute(parameters);
    }

    public event EventHandler CanExecuteChanged
    {
        add { CommandManager.RequerySuggested += value; }
        remove { CommandManager.RequerySuggested -= value; }
    }

    public void Execute(object parameters)
    {
        _execute(parameters);
    }

    #endregion // ICommand Members
}

Answer 1

你在SaveCommand的{{1}}部分犯了一个错误/拼写错误，你应该改变

get至if (_saveCommand != null)

Answer 2

您的CanSave方法返回false。

考虑解决这个问题。

MVVM WPF按钮命令绑定 - RelayCommand

2 个答案: