ArgumentOutofRangeException

Random r = new Random();
        int InvadorNumberA=r.Next(0,5);
        int randomShot = r.Next(5);
        List<Invaders> invadersShooting = new List<Invaders>();
        Invaders invaderA=new Invaders();
        var invaderByLocationX = from invadersSortByLocation in invaders
                                 group invadersSortByLocation by invadersSortByLocation.Location.Y
                                 into invaderGroup
                                 orderby invaderGroup.Key
                                 select invaderGroup;
       invadersShooting = invaderByLocationX.Last().ToList();
     try
       {
           invaderA = invadersShooting[InvadorNumberA];// constantly being thrown there. i cant catch the exception.. so i guess it is being thrown somewhere else. any idea on how i stop it from being thrown?
       }
        catch(ArgumentOutOfRangeException dd)
       {
           invaderA = invadersShooting[0];
       }

堆栈跟踪

" at System.ThrowHelper. "'r'n at System.ThrowHelper.ThrowArgumentOutOfRangeException()'r'n at System.Collections.Generic.List ' 1.使用实例get_Item(Int32 index)'r'n at WindowsFormsApplication1.Game.ReturnFire() in D:'Documents and Settings'Dima'My Documents'Visual Studio 2008'Projects'SpaceInvaders'SpaceInvaders'SpaceInvadorGame'Game.cs:line 444"

目标站点

{空白ThrowArgumentOutOfRangeException(系统。ExceptionArgument System.ExceptionResource)}

更多信息:

{"Index was out of range. Must be non-negative and less than the size of the collection.'r'nParameter name: index"}

{"索引超出范围。必须非负且小于集合的大小。'r'nParameter name: index"}

我通过简单地执行

来摆脱异常

 invadersShooting = invaderByLocationX.Last().ToList();
           invaderA = invadersShooting[r.Next(0,invadersShooting.Count)];

但是我仍然很好奇，在哪里抛出了异常…嗯

invaderA = invadersShooting[InvadorNumberA];
invaderA = invadersShooting[0];