GeekDesk/Command/DelegateCommand.cs

// Developed by doiTTeam => devdoiTTeam@gmail.com
using System;
using System.Windows.Input;

namespace DraggAnimatedPanelExample
{
    /// <summary>
    ///   An <see cref = "ICommand" /> whose delegates can be attached for <see cref = "Execute" /> and <see cref = "CanExecute" />.
    ///   It also implements the <see cref = "IActiveAware" /> interface, which is useful when registering this command in a <see cref = "CompositeCommand" /> that monitors command's activity.
    /// </summary>
    /// <typeparam name = "T">Parameter type.</typeparam>
    /// <remarks>
    ///   The constructor deliberately prevent the use of value types.
    ///   Because ICommand takes an object, having a value type for T would cause unexpected behavior when CanExecute(null) is called during XAML initialization for command bindings.
    ///   Using default(T) was considered and rejected as a solution because the implementor would not be able to distinguish between a valid and defaulted values.
    ///   <para />
    ///   Instead, callers should support a value type by using a nullable value type and checking the HasValue property before using the Value property.
    ///   <example>
    ///     <code>
    ///       public MyClass()
    ///       {
    ///       this.submitCommand = new DelegateCommand&lt;int?&gt;(this.Submit, this.CanSubmit);
    ///       }
    /// 
    ///       private bool CanSubmit(int? customerId)
    ///       {
    ///       return (customerId.HasValue &amp;&amp; customers.Contains(customerId.Value));
    ///       }
    ///     </code>
    ///   </example>
    /// </remarks>
    public class DelegateCommand<T> : DelegateCommandBase
    {
        /// <summary>
        ///   Initializes a new instance of <see cref = "DelegateCommand{T}" />.
        /// </summary>
        /// <param name = "executeMethod">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 DelegateCommand(Action<T> executeMethod)
            : this(executeMethod, (o) => true)
        {
        }

        /// <summary>
        ///   Initializes a new instance of <see cref = "DelegateCommand{T}" />.
        /// </summary>
        /// <param name = "executeMethod">Delegate to execute when Execute is called on the command.  This can be null to just hook up a CanExecute delegate.</param>
        /// <param name = "canExecuteMethod">Delegate to execute when CanExecute is called on the command.  This can be null.</param>
        /// <exception cref = "ArgumentNullException">When both <paramref name = "executeMethod" /> and <paramref name = "canExecuteMethod" /> ar <see langword = "null" />.</exception>
        public DelegateCommand(Action<T> executeMethod, Func<T, bool> canExecuteMethod)
            : base((o) => executeMethod((T)o), (o) => canExecuteMethod((T)o))
        {
            if (executeMethod == null || canExecuteMethod == null)
                throw new ArgumentNullException("executeMethod");
        }

        ///<summary>
        ///  Determines if the command can execute by invoked the <see cref = "Func{T,Bool}" /> provided during construction.
        ///</summary>
        ///<param name = "parameter">Data used by the command to determine if it can execute.</param>
        ///<returns>
        ///  <see langword = "true" /> if this command can be executed; otherwise, <see langword = "false" />.
        ///</returns>
        public bool CanExecute(T parameter)
        {
            return base.CanExecute(parameter);
        }

        ///<summary>
        ///  Executes the command and invokes the <see cref = "Action{T}" /> provided during construction.
        ///</summary>
        ///<param name = "parameter">Data used by the command.</param>
        public void Execute(T parameter)
        {
            base.Execute(parameter);
        }
    }

    /// <summary>
    ///   An <see cref = "ICommand" /> whose delegates do not take any parameters for <see cref = "Execute" /> and <see cref = "CanExecute" />.
    /// </summary>
    /// <seealso cref = "DelegateCommandBase" />
    /// <seealso cref = "DelegateCommand{T}" />
    public class DelegateCommand : DelegateCommandBase
    {
        /// <summary>
        ///   Creates a new instance of <see cref = "DelegateCommand" /> with the <see cref = "Action" /> to invoke on execution.
        /// </summary>
        /// <param name = "executeMethod">The <see cref = "Action" /> to invoke when <see cref = "ICommand.Execute" /> is called.</param>
        public DelegateCommand(Action executeMethod) : this(executeMethod, () => true)
        {
        }

        /// <summary>
        ///   Creates a new instance of <see cref = "DelegateCommand" /> with the <see cref = "Action" /> to invoke on execution
        ///   and a <see langword = "Func" /> to query for determining if the command can execute.
        /// </summary>
        /// <param name = "executeMethod">The <see cref = "Action" /> to invoke when <see cref = "ICommand.Execute" /> is called.</param>
        /// <param name = "canExecuteMethod">The <see cref = "Func{TResult}" /> to invoke when <see cref = "ICommand.CanExecute" /> is called</param>
        public DelegateCommand(Action executeMethod, Func<bool> canExecuteMethod)
            : base((o) => executeMethod(), (o) => canExecuteMethod())
        {
            if (executeMethod == null || canExecuteMethod == null)
                throw new ArgumentNullException("executeMethod");
        }


        ///<summary>
        ///  Executes the command.
        ///</summary>
        public void Execute()
        {
            Execute(null);
        }

        /// <summary>
        ///   Determines if the command can be executed.
        /// </summary>
        /// <returns>Returns <see langword = "true" /> if the command can execute,otherwise returns <see langword = "false" />.</returns>
        public bool CanExecute()
        {
            return CanExecute(null);
        }
    }
}