以编程方式添加到 DataGridView 的 ComboBox 直到单元格失去焦点然后再次单击后才会打开

Question

在 C# WinForms 项目中，我从 DataTable 填充 DGV。当用户单击其中一列的单元格时，我需要填充 ComboBox 并单击一次打开它。

但是，只有当相关单元格失去焦点（单击表单上的其他位置）然后重新获得焦点（再次单击该单元格）时，CBO 才会打开 - 并且只有在单击 CBO 的向下箭头时才会打开，如果CBO 的文本被点击。当点击 CBO 的文本时，我还需要打开 CBO。

private void dgvCategories_Click(Object sender, DataGridViewCellEventArgs e)
{
    try
    {
        // Prevent code from executing if user clicks on a cell that already has a CBO
        if (e.ColumnIndex == 5 && !(dgvCategories.Rows[e.RowIndex].Cells[e.ColumnIndex].GetType().Name == "DataGridViewComboBoxCell"))
        {
            // Get fields to build New Value query
            List<string> lsNewValuesResult = new List<string>();
            string strCategory = dtCategories.Rows[e.RowIndex][1].ToString();
            string strCompanyName = cboSelectCompany.Text;
            string strQueryGetNewValuesValidationInfo = "SELECT validationdb, validationtable, validationfield, validationfield2, validationvalue2" +
                                                    " FROM masterfiles.categories" +
                                                    " WHERE category = @category";

            // Pass validation info query to db and return list of New Values
            db getListOfNewValues = new db();
            lsNewValuesResult = getListOfNewValues.GetNewValuesList(strQueryGetNewValuesValidationInfo, strCategory, strCompanyName);

            // Create CBO object
            DataGridViewComboBoxCell cboNewValueList = new DataGridViewComboBoxCell();

            //Populate the combobox with the list of New Values
            foreach (string strListItem in lsNewValuesResult) cboNewValueList.Items.Add(strListItem);

            // Bind the CBO to the DGV
            dgvCategories[e.ColumnIndex, e.RowIndex] = cboNewValueList;

            var editingControl = dgvCategories.EditingControl as DataGridViewComboBoxEditingControl;
            if (editingControl != null) editingControl.DroppedDown = true;
        }
    }
    catch (Exception ex)
    {
        Console.WriteLine("dgvCategories_Click Exception: " + ex.Message);
    }

}

DataGridViewEditMode 设置为EditOnEnter，DataGrieViewSelectionMode 设置为CellSelect。

最后的两行来自 SO Question，“DataGridViewComboBoxColumn - Have to click cell twice to display combo box”

我不知道还能尝试什么...

Answer 1

如果您考虑使用CellBeginEdit 事件来解决您的问题，那么您可以使用下一种方法：

private void dgvCategories_CellBeginEdit(Object sender, DataGridViewCellCancelEventArgs e)
{
    if (e.ColumnIndex == 5)
    {
        if (dgvCategories.Rows[e.RowIndex].Cells[e.ColumnIndex].GetType().Name != "DataGridViewComboBoxCell")
        {
            // Bind combobox to dgv and than bind new values datasource to combobox
            DataGridViewComboBoxCell cboNewValueList = new DataGridViewComboBoxCell();

            // Get fields to build New Value query
            List<string> lsNewValuesResult = getCboValues();

            //Populate the combobox with the list of New Values
            foreach (string strListItem in lsNewValuesResult)
            {
                cboNewValueList.Items.Add(strListItem);
            }

            // Store current cell value into ComboBox cell. It is for convenience.
            cboNewValueList.Value = dgvCategories[e.ColumnIndex, e.RowIndex].Value;

            // Cancel current BeginEdit event because it occurs on the cell of type TextBox.
            // Later we'll launch another BeginEdit event on cell of type ComboBox.
            e.Cancel = true;

            // BeginInvoke is needed because:
            // 1. there is a known problem with DataGridView:
            //   - https://stackoverflow.com/questions/5114668/why-is-my-bound-datagridview-throwing-an-operation-not-valid-because-it-results
            //   - https://stackoverflow.com/questions/26522927/how-to-evade-reentrant-call-to-setcurrentcelladdresscore/26527759#26527759
            // 2. current cell has type TextBox, but we want to change its type to
            //   ComboBox and then begin editing ComboBox.
            BeginInvoke(new Action(
                () =>
                {
                    // Change type of current cell to ComboBox.
                    dgvCategories[e.ColumnIndex, e.RowIndex] = cboNewValueList;
                    // Begin editing of the ComboBox cell.
                    dgvCategories.BeginEdit(true);

                    // Here (after BeginEdit) the type of the cell is ComboBox.
                    // Automatically drop down ComboBox cell.
                    if (dgvCategories.EditingControl != null)
                        ((DataGridViewComboBoxEditingControl)dgvCategories.EditingControl).DroppedDown = true;
                }));
        }
        else
        {
            // If current cell is already of type ComboBox then we simply drop down it.
            BeginInvoke(new Action(
                () =>
                {
                    if (dgvCategories.EditingControl != null)
                        ((DataGridViewComboBoxEditingControl)dgvCategories.EditingControl).DroppedDown = true;
                }));
        }
    }
}

以下是对这种方法的解释：

• 如果CellBeginEdit 事件发生在TextBox 类型的单元格上，我们取消此事件，然后：
  • 将当前单元格类型更改为ComboBox;
  • 为当前ComboBox 单元启动CellBeginEdit 事件；
  • 自动下拉当前ComboBox单元格；
• 如果CellBeginEdit 事件发生在ComboBox 类型的单元格上，我们只需将其下拉即可；
• 我们使用BeginInvoke 更改当前单元格的类型，然后开始编辑，因为：
  • DataGridView（1、2）存在一个已知问题，迫使我们使用BeginInvoke：
  • 当事件CellBeginEdit 完成时，单元格的类型会发生变化。

使用CellBeginEdit 的方法还有下一个好处：它可以更改单元格类型，无论是用户使用鼠标还是键盘导航到单元格。

---

另一种方法是使用CellStateChanged事件：

private void dgvCategories_CellStateChanged(object sender, DataGridViewCellStateChangedEventArgs e)
{
    if (e.StateChanged == DataGridViewElementStates.Selected)
    {
        int col = e.Cell.ColumnIndex;
        int row = e.Cell.RowIndex;

        if (col == 5)
        {
            if (dgvCategories.Rows[row].Cells[col].GetType().Name != "DataGridViewComboBoxCell")
            {
                // Bind combobox to dgv and than bind new values datasource to combobox
                DataGridViewComboBoxCell cboNewValueList = new DataGridViewComboBoxCell();

                // Get fields to build New Value query
                List<string> lsNewValuesResult = getCboValues();

                //Populate the combobox with the list of New Values
                foreach (string strListItem in lsNewValuesResult)
                {
                    cboNewValueList.Items.Add(strListItem);
                }

                // 
                cboNewValueList.Value = dgvCategories[col, row].Value;
                dgvCategories[col, row] = cboNewValueList;

                // To drop down current cell we must call BeginInvoke,
                // because in the CellStateChanged event handler
                // dgvCategories.EditingControl is null.
                BeginInvoke(new Action(
                    () =>
                    {
                        if (dgvCategories.EditingControl != null)
                            ((DataGridViewComboBoxEditingControl) dgvCategories.EditingControl).DroppedDown = true;
                    }));
            }
            else
            {
                // If current cell is already ComboBox we simply drop it down.
                BeginInvoke(new Action(
                    () =>
                    {
                        if (dgvCategories.EditingControl != null)
                            ((DataGridViewComboBoxEditingControl)dgvCategories.EditingControl).DroppedDown = true;
                    }));
            }
        }
    }
}