ICommand 介面

定義

public interface class ICommand

/// [Windows.Foundation.Metadata.ContractVersion(Microsoft.UI.Xaml.WinUIContract, 65536)]
/// [Windows.Foundation.Metadata.Guid(3853464898, 51815, 16513, 153, 91, 112, 157, 209, 55, 146, 223)]
struct ICommand

[Windows.Foundation.Metadata.ContractVersion(typeof(Microsoft.UI.Xaml.WinUIContract), 65536)]
[Windows.Foundation.Metadata.Guid(3853464898, 51815, 16513, 153, 91, 112, 157, 209, 55, 146, 223)]
public interface ICommand

Public Interface ICommand

衍生

Microsoft.UI.Xaml.Input.XamlUICommand

屬性

ContractVersionAttribute GuidAttribute

範例

在這裡，我們定義了一個指令，簡單地將其功能轉發給其他物件。

完整應用程式請參閱 UI 基礎（XAML）範例 。

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Input;
namespace AppUIBasics.Common
{
    /// <summary>
    /// A 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'.
    /// RaiseCanExecuteChanged needs to be called whenever
    /// CanExecute is expected to return a different value.
    /// </summary>
    public class RelayCommand : ICommand
    {
        private readonly Action _execute;
        private readonly Func<bool> _canExecute;
        /// <summary>
        /// Raised when RaiseCanExecuteChanged is called.
        /// </summary>
        public event EventHandler CanExecuteChanged;
        /// <summary>
        /// Creates a new command that can always execute.
        /// </summary>
        /// <param name="execute">The execution logic.</param>
        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;
        }
        /// <summary>
        /// Determines whether this RelayCommand 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();
        }
        /// <summary>
        /// Executes the RelayCommand on the current command target.
        /// </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>
        public void Execute(object parameter)
        {
            _execute();
        }
        /// <summary>
        /// Method used to raise the CanExecuteChanged event
        /// to indicate that the return value of the CanExecute
        /// method has changed.
        /// </summary>
        public void RaiseCanExecuteChanged()
        {
            var handler = CanExecuteChanged;
            if (handler != null)
            {
                handler(this, EventArgs.Empty);
            }
        }
    }
}

備註

XamlUICommand 為 C++ 或 System.Windows 實作此ICommand介面。C# 的 Input.ICommand（新增各種 UI 屬性、方法與事件）。

舉個基本例子，請參考 按鈕 控制項，使用者點擊時會呼叫指令。 你可以用兩種方式管理指揮體驗：

• 處理事件Click
• 將屬性 Command 綁定到描述指令邏輯的 ICommand 實作

另請參閱

• XamlUICommand
• StandardUICommand
• 指揮基礎
• 在 Windows 應用程式中使用 StandardUICommand、XamlUICommand 和 ICommand 進行指令