protected virtual void OnExecuting(CommandExecutingEventArgs e)
{
var executing = this.Executing;
if (executing != null)
{
executing(this, e);
}
}
/// <summary>
/// 执行命令。
/// </summary>
/// <param name="parameter">执行命令的参数。</param>
/// <returns>返回执行的返回结果。</returns>
/// <remarks>
/// <para>本方法的实现中首先调用<see cref="CanExecute"/>方法，以确保阻止非法的调用。</para>
/// </remarks>
protected virtual object Execute(object parameter)
{
//在执行之前首先判断是否可以执行
if (!this.CanExecute(parameter))
{
return(null);
}
//创建事件参数对象
var executingArgs = new CommandExecutingEventArgs(parameter, null);
//激发“Executing”事件
this.OnExecuting(executingArgs);
//如果事件处理程序要取消后续操作，则返回退出
if (executingArgs.Cancel)
{
return(executingArgs.Result);
}
object result = executingArgs.Result;
CommandExecutedEventArgs executedArgs;
try
{
//执行具体的工作
result = this.OnExecute(parameter);
}
catch (Exception ex)
{
//创建事件参数对象
executedArgs = new CommandExecutedEventArgs(parameter, ex);
//激发“Executed”事件
this.OnExecuted(executedArgs);
if (!executedArgs.ExceptionHandled)
{
throw;
}
return(executedArgs.Result);
}
//创建事件参数对象
executedArgs = new CommandExecutedEventArgs(parameter, result);
//激发“Executed”事件
this.OnExecuted(executedArgs);
//返回执行成功的结果
return(executedArgs.Result);
}
/// <summary>
/// 执行命令。
/// </summary>
/// <param name="parameter">执行命令的参数。</param>
/// <returns>返回执行的返回结果。</returns>
/// <remarks>
/// <para>本方法的实现中首先调用<see cref="CanExecute"/>方法，以确保阻止非法的调用。</para>
/// </remarks>
protected virtual object Execute(object parameter)
{
//在执行之前首先判断是否可以执行
if(!this.CanExecute(parameter))
return null;
//创建事件参数对象
var executingArgs = new CommandExecutingEventArgs(parameter, null);
//激发“Executing”事件
this.OnExecuting(executingArgs);
//如果事件处理程序要取消后续操作，则返回退出
if(executingArgs.Cancel)
return executingArgs.Result;
object result = executingArgs.Result;
CommandExecutedEventArgs executedArgs;
try
{
//执行具体的工作
result = this.OnExecute(parameter);
}
catch(Exception ex)
{
//创建事件参数对象
executedArgs = new CommandExecutedEventArgs(parameter, ex);
//激发“Executed”事件
this.OnExecuted(executedArgs);
if(!executedArgs.ExceptionHandled)
throw;
return executedArgs.Result;
}
//创建事件参数对象
executedArgs = new CommandExecutedEventArgs(parameter, result);
//激发“Executed”事件
this.OnExecuted(executedArgs);
//返回执行成功的结果
return executedArgs.Result;
}
protected virtual void OnExecuting(CommandExecutingEventArgs e)
{
var executing = this.Executing;
if(executing != null)
executing(this, e);
}
protected virtual void OnExecuting(CommandExecutingEventArgs e)
{
this.Executing?.Invoke(this, e);
}