绑定到 DataRowView 的 Winforms 控件更改行值但不更改 RowState

Question

一个简单的 WinForms 应用程序，用于了解控件数据绑定。下面的代码来自名为 frmMain 并包含 TextBoxes txtFirstName 和 txtLastName，以及名为 nudRow 的数字向上/向下。编辑文本框中的文本并更改行，我注意到以前的 DataRow 在“建议”行版本中的值发生了更改（例如 _Tbl.Rows[3][1, DataRowVersion.Proposed]），但 RowState 仍然是 '不变”。我错过了什么会使“提议”变为“当前”并改变 RowState？注释掉的“DataSourceUpdateMode”没有任何区别。

我也很模糊为什么我需要继续重置 TextBox DataBindings 而不是仅在数值上/下值更改事件中设置 DataRowView (_CurRow)。

编辑：我想我很清楚我的问题是：为什么 RowState 没有改变？此外，是否有通常用于处理“建议”值和更改 RowState 的标准模式（验证或其他东西）？顺便说一句，我想知道为什么我必须重建数据绑定，而不是仅仅更改已经绑定的东西的值，但也许这需要是一个单独的问题。

EDIT2：查看有关 DataRowVersion.Proposed 的一些文档后，看起来我应该在我的数值上/下值更改事件中添加类似下面的代码。不幸的是，在帖子被搁置时，我无法回答自己的问题...

if (_CurRow.Row.HasVersion(DataRowVersion.Proposed))
{
  // Do validation stuff then
  if(isValid)
  {
    _CurRow.Row.EndEdit();
  }
  else
  {
    _CurRow.Row.CancelEdit();
  }
}

就个人而言，我会验证表单输入控件中的每个用户输入，但我现在知道，即使在控件中还原原始值也会在 DataRow 中创建一个建议的版本。

private DataRowView _CurRow = null;
private DataTable _Tbl = null;

private const string COL_NAME_ROW = "Row No.";
private const string COL_NAME_FIRST = "First Name";
private const string COL_NAME_LAST = "Last Name";

public frmMain()
{
  DataRow dr;

  InitializeComponent();
  _Tbl = new DataTable();
  _Tbl.Columns.Add(COL_NAME_ROW, typeof(int));
  _Tbl.Columns.Add(COL_NAME_FIRST, typeof(string));
  _Tbl.Columns.Add(COL_NAME_LAST, typeof(string));
  dr = _Tbl.NewRow();
  dr[COL_NAME_ROW] = 0;
  dr[COL_NAME_FIRST] = "Alan";
  dr[COL_NAME_LAST] = "Ladd";
  _Tbl.Rows.Add(dr);
  dr = _Tbl.NewRow();
  dr[COL_NAME_ROW] = 1;
  dr[COL_NAME_FIRST] = "Boris";
  dr[COL_NAME_LAST] = "Yeltsin";
  _Tbl.Rows.Add(dr);
  dr = _Tbl.NewRow();
  dr[COL_NAME_ROW] = 2;
  dr[COL_NAME_FIRST] = "Cab";
  dr[COL_NAME_LAST] = "Calloway";
  _Tbl.Rows.Add(dr);
  dr = _Tbl.NewRow();
  dr[COL_NAME_ROW] = 3;
  dr[COL_NAME_FIRST] = "David";
  dr[COL_NAME_LAST] = "Letterman";
  _Tbl.Rows.Add(dr);
  _Tbl.AcceptChanges();

}

private void frmMain_Shown(object sender, EventArgs e)
{
  _CurRow = _Tbl.DefaultView[0];
  this.txtFirstName.DataBindings.Add("Text", _CurRow, COL_NAME_FIRST); //,
  //false, DataSourceUpdateMode.OnPropertyChanged);
  this.txtLastName.DataBindings.Add("Text", _CurRow, COL_NAME_LAST); //,
  //false, DataSourceUpdateMode.OnPropertyChanged);
  //this.nudRow.DataBindings.Add("Value", _Tbl, COL_NAME_ROW);
}

private void nudRow_ValueChanged(object sender, EventArgs e)
{
  // Previous row has modified (proposed) data here, but unchanged RowState
  _CurRow = _Tbl.DefaultView[(int)this.nudRow.Value];
  this.txtFirstName.DataBindings.Clear();
  this.txtFirstName.DataBindings.Add("Text", _CurRow, COL_NAME_FIRST); //,
    //false, DataSourceUpdateMode.OnPropertyChanged);
  this.txtLastName.DataBindings.Clear();
  this.txtLastName.DataBindings.Add("Text", _CurRow, COL_NAME_LAST); //,
  //false, DataSourceUpdateMode.OnPropertyChanged);

}

Answer 1

编辑绑定控件会导致 DataRow 上的 BeginEdit 应使用 EndEdit 或 CancelEdit 关闭。下面的代码使用一种可能的解决方案进行了修改。

private DataRowView _CurRow = null;
private DataTable _Tbl = null;

private const string COL_NAME_ROW = "Row No.";
private const string COL_NAME_FIRST = "First Name";
private const string COL_NAME_LAST = "Last Name";

public frmMain()
{
  DataRow dr;

  InitializeComponent();
  _Tbl = new DataTable();
  _Tbl.Columns.Add(COL_NAME_ROW, typeof(int));
  _Tbl.Columns.Add(COL_NAME_FIRST, typeof(string));
  _Tbl.Columns.Add(COL_NAME_LAST, typeof(string));
  dr = _Tbl.NewRow();
  dr[COL_NAME_ROW] = 0;
  dr[COL_NAME_FIRST] = "Alan";
  dr[COL_NAME_LAST] = "Ladd";
  _Tbl.Rows.Add(dr);
  dr = _Tbl.NewRow();
  dr[COL_NAME_ROW] = 1;
  dr[COL_NAME_FIRST] = "Boris";
  dr[COL_NAME_LAST] = "Yeltsin";
  _Tbl.Rows.Add(dr);
  dr = _Tbl.NewRow();
  dr[COL_NAME_ROW] = 2;
  dr[COL_NAME_FIRST] = "Cab";
  dr[COL_NAME_LAST] = "Calloway";
  _Tbl.Rows.Add(dr);
  dr = _Tbl.NewRow();
  dr[COL_NAME_ROW] = 3;
  dr[COL_NAME_FIRST] = "David";
  dr[COL_NAME_LAST] = "Letterman";
  _Tbl.Rows.Add(dr);
  _Tbl.AcceptChanges();

}

private void frmMain_Shown(object sender, EventArgs e)
{
  _CurRow = _Tbl.DefaultView[0];
  this.txtFirstName.DataBindings.Add("Text", _CurRow, COL_NAME_FIRST); //,
  //false, DataSourceUpdateMode.OnPropertyChanged);
  this.txtLastName.DataBindings.Add("Text", _CurRow, COL_NAME_LAST); //,
  //false, DataSourceUpdateMode.OnPropertyChanged);
  //this.nudRow.DataBindings.Add("Value", _Tbl, COL_NAME_ROW);
}

private void nudRow_ValueChanged(object sender, EventArgs e)
{
  bool? hasChanged = null;
  // Previous row has modified (proposed) data here, but unchanged
  // RowState. Need to end or cancel the BeginEdit caused by
  // editing the bound control in order to update the RowState to
  // Modified and push Proposed value to Current (EndEdit) or
  // leave the RowState Unchanged (CancelEdit)
  hasChanged = this.RowHasChanged(_CurRow.Row);
  if (!hasChanged.HasValue)
  {
    // Didn't have proposed version so no-op
  }
  else if (hasChanged.Value)
  {
    _CurRow.Row.EndEdit();
  }
  else
  {
    _CurRow.Row.CancelEdit();
  }
  _CurRow = _Tbl.DefaultView[(int)this.nudRow.Value];
  this.txtFirstName.DataBindings.Clear();
  this.txtFirstName.DataBindings.Add("Text", _CurRow, COL_NAME_FIRST);
  this.txtLastName.DataBindings.Clear();
  this.txtLastName.DataBindings.Add("Text", _CurRow, COL_NAME_LAST);

}

// This is necessary because reverting values still causes
// row to have proposed version, but isn't a true change
private bool RowHasChanged(DataRow DataRowObj)
{
  bool retVal = false;

  if (!DataRowObj.HasVersion(DataRowVersion.Proposed)) return retVal;
  for (int ii = 0; ii < _CurRow.Row.ItemArray.Length; ii++)
  {
    if (!object.Equals(
            _CurRow.Row[ii, DataRowVersion.Current],
            _CurRow.Row[ii, DataRowVersion.Proposed]))
    {
      retVal = true;
      break;
    }
  }
  if (!retVal.HasValue) retVal = false;
  return retVal;

}