命令用于 将语义和调用命令的对象与执行命令
的逻辑分开，即，将UI组件与需要在命令调用时执行的逻辑分开。因此，您可以使用测试用例分别测试业务逻辑，并且您的UI代码可以松散地耦合到业务逻辑。

话虽如此，让我们一个接一个地选择您的问题：

它做什么工作？

我已在上面添加了详细信息。希望它清除命令的用法。

它可以用于我表格中的所有命令吗？

一些控件公开了Command
DependencyProperty，如Button，MenuItem等，这些控件已注册了一些默认事件。对于Button，这是Click事件。因此，如果将ICommandViewModel中声明的内容与Button的Command
DP 绑定，则只要单击button就会调用它。

对于其他事件，可以使用绑定Interactivity triggers。请参阅此处的示例，了解如何ICommand在ViewModel中使用它们进行绑定。

当未填写某些文本框时，如何使按钮禁用？

您发布的链接未提供的完整实现RelayCommand。它缺少设置CanExecute谓词的重载构造函数，该谓词在启用/禁用命令绑定到的UI控件中起着关键作用。

CanExecute如果任何绑定的属性为null或为空，则将TextBoxes与ViewModel和委托中的某些属性绑定将返回false，这将自动禁用将命令绑定到的控件。

全面实施RelayCommand：

public class RelayCommand<T> : ICommand
{
    #region Fields

    readonly Action<T> _execute = null;
    readonly Predicate<T> _canExecute = null;

    #endregion

    #region Constructors

    /// <summary>
    /// Initializes a new instance of <see cref="DelegateCommand{T}"/>.
    /// </summary>
    /// <param name="execute">Delegate to execute when Execute is called on the command.  This can be null to just hook up a CanExecute delegate.</param>
    /// <remarks><seealso cref="CanExecute"/> will always return true.</remarks>
    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

    #region ICommand Members

    ///<summary>
    ///Defines the method that determines whether the command can execute in its current state.
    ///</summary>
    ///<param name="parameter">Data used by the command.  If the command does not require data to be passed, this object can be set to null.</param>
    ///<returns>
    ///true if this command can be executed; otherwise, false.
    ///</returns>
    public bool CanExecute(object parameter)
    {
        return _canExecute == null ? true : _canExecute((T)parameter);
    }

    ///<summary>
    ///Occurs when changes occur that affect whether or not the command should execute.
    ///</summary>
    public event EventHandler CanExecuteChanged
    {
        add { CommandManager.RequerySuggested += value; }
        remove { CommandManager.RequerySuggested -= value; }
    }

    ///<summary>
    ///Defines the method to be called when the command is invoked.
    ///</summary>
    ///<param name="parameter">Data used by the command. If the command does not require data to be passed, this object can be set to <see langword="null" />.</param>
    public void Execute(object parameter)
    {
        _execute((T)parameter);
    }

    #endregion
}