Question

我有一个datagridview，左边有3个冻结列，然后我想要的第4列总是显示在右边。其余列显示在第3列和第4列之间，并在其标题中编号（带有1,2,3,4 ......）。我允许用户重新排序这些列，但我希望列标题保持数字顺序。这个想法是用户应该将其视为重新排序列中的数据，而不是列本身。第4列标有＆＃34; New＆＃34;，如果用户试图将数据放入其中，则会创建一个新列并将数据添加到其中，这也是我希望它总是在右边的原因之一。

为实现此目的，我使用以下ColumnDisplayIndexChanged事件：

private void dgvTreeLevels_ColumnDisplayIndexChanged(object sender, DataGridViewColumnEventArgs e) {
    switch(e.Column.Index) {
       case 0:
       case 1:
       case 2: //prevents columns 0, 1, 2 from being reordered, (freezing just prevents them from being switched with 3+)
          SynchronizationContext.Current.Post(delegate(object o) {
             if (e.Column.DisplayIndex != e.Column.Index) e.Column.DisplayIndex = e.Column.Index;
          }, null);
          break;
       case 3: //Displays always on the right
          SynchronizationContext.Current.Post(delegate(object o) {
             if (e.Column.DisplayIndex != dgvTreeLevels.Columns.Count - 1)
                e.Column.DisplayIndex = dgvTreeLevels.Columns.Count - 1;
          }, null);
          break;
       default: //Numbered columns
          e.Column.HeaderText = (e.Column.DisplayIndex - 2).ToString();
          break;
    }
 }

大部分时间它工作正常。但偶尔行

              e.Column.HeaderText = (e.Column.DisplayIndex - 2).ToString();

正在抛出一个ArgumentOutOfRangeException，声明索引超出范围。由于它没有设置任何索引，因此这尤其令人困惑。我无法可靠地创建错误。当我测试功能时，它会偶尔弹出。我认为这可能与尝试将编号列移到最右边有关，但是当我正在做其他事情时，错误会弹出。

检入调试器会显示行中的所有元素都已定义并具有正确的值。我不知道为什么会有错误。堆栈跟踪是

System.ArgumentOutOfRangeException was unhandled
  Message="Index was out of range. Must be non-negative and less than the size of the collection.\r\nParameter name: index"
  Source="mscorlib"
  ParamName="index"
  StackTrace:
       at System.Collections.ArrayList.get_Item(Int32 index)
       at System.Windows.Forms.DataGridViewColumnCollection.get_Item(Int32 index)
       at System.Windows.Forms.DataGridView.GetColumnDisplayRectanglePrivate(Int32 columnIndex, Boolean cutOverflow)
       at System.Windows.Forms.DataGridView.GetCellDisplayRectangle(Int32 columnIndex, Int32 rowIndex, Boolean cutOverflow)
       at System.Windows.Forms.DataGridView.GetCellAdjustedDisplayRectangle(Int32 columnIndex, Int32 rowIndex, Boolean cutOverflow)
       at System.Windows.Forms.DataGridView.InvalidateCellPrivate(Int32 columnIndex, Int32 rowIndex)
       at System.Windows.Forms.DataGridView.OnColumnHeaderGlobalAutoSize(Int32 columnIndex)
       at System.Windows.Forms.DataGridView.OnCellValueChanged(DataGridViewCellEventArgs e)
       at System.Windows.Forms.DataGridViewColumnHeaderCell.SetValue(Int32 rowIndex, Object value)
       at System.Windows.Forms.DataGridViewColumn.set_HeaderText(String value)
       at Customizable_Reports.frmReport.dgvTreeLevels_ColumnDisplayIndexChanged(Object sender, DataGridViewColumnEventArgs e)
       at System.Windows.Forms.DataGridView.FlushDisplayIndexChanged(Boolean raiseEvent)
       at System.Windows.Forms.DataGridView.CorrectColumnDisplayIndexesAfterDeletion(DataGridViewColumn dataGridViewColumn)
       at System.Windows.Forms.DataGridView.OnRemovedColumn_PreNotification(DataGridViewColumn dataGridViewColumn)
       at System.Windows.Forms.DataGridViewColumnCollection.RemoveAtInternal(Int32 index, Boolean force)
       at System.Windows.Forms.DataGridViewColumnCollection.RemoveAt(Int32 index)
       at Customizable_Reports.frmReport.RemoveEmptyColumns()
       at Customizable_Reports.frmReport.dgvTreeLevels_CellClick(Object sender, DataGridViewCellEventArgs e)
       at System.Windows.Forms.DataGridView.OnMouseClick(MouseEventArgs e)
       at System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks)
       at System.Windows.Forms.Control.WndProc(Message& m)
       at System.Windows.Forms.DataGridView.WndProc(Message& m)
       at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
       at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
       at System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg)
       at System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(Int32 dwComponentID, Int32 reason, Int32 pvLoopData)
       at System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context)
       at System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context)
       at Customizable_Reports.Program.Main()
       at System.AppDomain._nExecuteAssembly(Assembly assembly, String[] args)
       at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()
       at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
       at System.Threading.ThreadHelper.ThreadStart()
  InnerException:

Answer 1

进一步测试显示，当较高编号的列移动到较低编号的列前面时出现错误，之后被删除。如果由于删除而在ColumnDisplayIndexChanged事件中更新了较低编号列的标题文本，则会发生错误。

您可以通过创建一个新的Winform应用程序来测试它，在表单上放置一个包含两列的datagridview，并允许用户对它们进行重新排序。添加一个按钮和以下两个事件：

  private void button1_Click(object sender, EventArgs e) {
     dataGridView1.Columns.RemoveAt(1);
  }

  private void dataGridView1_ColumnDisplayIndexChanged(object sender, DataGridViewColumnEventArgs e) {
     e.Column.HeaderText = e.Column.DisplayIndex.ToString();
  }

运行应用程序，拖动第1列前面的第2列，然后按按钮。请注意，必须为列提供唯一标头才能发生此错误。设置e.Column.HeaderText = "test";代替不会产生错误。

对我而言，这似乎是WinForms中的一个错误，而不是在这个编程中。但我不太清楚会发生什么事情。

将命令传递给当前同步上下文似乎可以解决问题：

SynchronizationContext.Current.Post(delegate(object o) {
     e.Column.HeaderText = e.Column.DisplayIndex.ToString();
}, null);

没有设置索引时，datagridview索引超出范围错误

1 个答案: