未处理 NullReferenceException错误

Question

本帖最后由 bulls5988 于 2011-11-09 10:48:06 编辑

Answer 1

public DataGridView userlist_load(DataGridView u_data)
{
....
}
这里面问题。
这种NullReference问题，他提示你的地方设个断点调试就知道！

Answer 2

这个填充DGV和保存修改数据 都没问题。都不会报错，只有这个刷新窗体才保存

Answer 3

 这个填充DGV和保存修改数据 都没问题。都不会报错，只有这个刷新窗体才报错

Answer 4

你在其它地方调用窗体的load事件处理函数？那个事件没有触发，那当然是null值。引用肯定出错啊。

Answer 5

你应该调用refresh.formload()而不是refresh.form_load()吧

Answer 6

并不是这样的，我这样写，public void form_load()
        {
            m_userlist users = new m_userlist();
            users.userlist_load(d_userlist);
        }也照样是提示: 未处理 System.NullReferenceException
  Message="未将对象引用设置到对象的实例。"
  Source="中影会员卡"
  StackTrace:
       在 中影会员卡.m_useredit.b_save_Click(Object sender, EventArgs e) 位置 C:\middlemovie\中影会员卡\m_useredit.cs:行号 172
       在 System.Windows.Forms.Control.OnClick(EventArgs e)
       在 System.Windows.Forms.Button.OnClick(EventArgs e)
       在 System.Windows.Forms.Button.OnMouseUp(MouseEventArgs mevent)
       在 System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks)
       在 System.Windows.Forms.Control.WndProc(Message& m)
       在 System.Windows.Forms.ButtonBase.WndProc(Message& m)
       在 System.Windows.Forms.Button.WndProc(Message& m)
       在 System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
       在 System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
       在 System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
       在 System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg)
       在 System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(Int32 dwComponentID, Int32 reason, Int32 pvLoopData)
       在 System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context)
       在 System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context)
       在 System.Windows.Forms.Form.ShowDialog(IWin32Window owner)
       在 System.Windows.Forms.Form.ShowDialog()
       在 中影会员卡.m_usermange.b_edit_Click(Object sender, EventArgs e) 位置 C:\middlemovie\中影会员卡\m_usermange.cs:行号 51
       在 System.Windows.Forms.Control.OnClick(EventArgs e)
       在 System.Windows.Forms.Button.OnClick(EventArgs e)
       在 System.Windows.Forms.Button.OnMouseUp(MouseEventArgs mevent)
       在 System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks)
       在 System.Windows.Forms.Control.WndProc(Message& m)
       在 System.Windows.Forms.ButtonBase.WndProc(Message& m)
       在 System.Windows.Forms.Button.WndProc(Message& m)
       在 System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
       在 System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
       在 System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
       在 System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg)
       在 System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(Int32 dwComponentID, Int32 reason, Int32 pvLoopData)
       在 System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context)
       在 System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context)
       在 System.Windows.Forms.Application.Run(Form mainForm)
       在 中影会员卡.Program.Main() 位置 C:\middlemovie\中影会员卡\Program.cs:行号 29
       在 System.AppDomain._nExecuteAssembly(Assembly assembly, String[] args)
       在 System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args)
       在 Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()
       在 System.Threading.ThreadHelper.ThreadStart_Context(Object state)
       在 System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
       在 System.Threading.ThreadHelper.ThreadStart()
  InnerException: 

Answer 7

找到啦，调用时少了:edit.Owner = this;

Answer 8

我说的是你在m_useredit.cs中应该调用refresh.formload()而不是refresh.form_load()。你在m_usermange.cs中把
public void form_load()
        {
            formload();
        }
改成
public void form_load()
  {
  m_userlist users = new m_userlist();
  users.userlist_load(d_userlist);
  }
那不是跟没改一样么。关键是你在m_useredit.cs中不能调用m_usermange.cs中的load事件处理函数