c#,winform，接收message，按下了w键，却没收到WM_KEYDOWN和WM_KEYUP

窗体布局

代码大概就是，导入了自己写的会hook所有线程的按键，并把按键信息以Message的形式发来这个窗体dll,按button1就是开始hook，button2停止hook，button3按照一定的格式把收到的Message的WParam属性的值显示出来。
部分代码如下

 const int WM_CHAR = 0x102;
const int WM_UNICHAR = 0X109;

const int VK_SHIFT = 16;
const int VK_CAPITAI = 20;

char[] ascii=new char[26]{'a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z'};

[DllImport(@"User32.dll")]
protected static extern short GetKeyState(int nVirtualKey);

protected override void WndProc(ref Message m)
    {
        bool IsRecord = true;
        int a = (int)m.WParam;
        if (a >= 65 && a <= 90)
        {
             Console.WriteLine("the m.Msg is : " + m.Msg + " \n");
             if (GetKeyState(VK_SHIFT) < 0 || (GetKeyState(VK_CAPITAI) != 0 ? true : false))
             {
                char c = ascii[a - 65];
                char d = (char)(c - 32);
                str = str + "the button you press is: " + d + " \n";
              }
              else str = str + "the button you press is: " + ascii[a - 65] + " \n";
      }

          base.WndProc(ref m);
    }

然后我只按下一次"w"键，如下图

上图这是后台输出，代码中有，但是收到的信息的id为0和3，即是WM_NULL和WM_MOVE，却不是收到WM_KEYDOWN和WM_KEYUP，但是此信息的WParam属性又是准确对应了键码，这是怎么回事？

keypreview属性设置了么？onkeypress重写了么？