DataGridView编辑模式下空单元格显下拉框及值获取异常问题

1. 清空单元格时自动展开下拉框 #

你之前的代码判断的是CurrentCell.Value，但编辑模式下这个值是编辑前的旧数据，不会实时跟着输入内容更新，所以删到空也触发不了下拉。改成直接读取ComboBox的实时文本就行：

修改ComboBox_KeyPress事件：

void ComboBox_KeyPress(object sender, KeyPressEventArgs e)
{
    var comboBox = sender as ComboBox;
    if (comboBox == null) return;

    // 退格键触发后检查文本是否为空
    if (e.KeyChar == '\b' && string.IsNullOrWhiteSpace(comboBox.Text.Trim()))
    {
        comboBox.DroppedDown = true;
    }
    else if (!string.IsNullOrWhiteSpace(comboBox.Text.Trim()))
    {
        comboBox.DroppedDown = false;
    }
}

另外，Delete键不会触发KeyPress，所以要加个KeyDown事件处理：

private void ComboBox_KeyDown(object sender, KeyEventArgs e)
{
    var comboBox = sender as ComboBox;
    if (comboBox == null) return;

    if (e.KeyCode == Keys.Delete && string.IsNullOrWhiteSpace(comboBox.Text.Trim()))
    {
        comboBox.DroppedDown = true;
    }
}

然后在EditingControlShowing里绑定这个KeyDown事件：

private void DataGridView_EditingControlShowing(object sender, DataGridViewEditingControlShowingEventArgs e)
{
    comboBoxHandler = e.Control as ComboBox;

    if (comboBoxHandler != null)
    {
        comboBoxHandler.IntegralHeight = false;   // 没有这个MaxDropDownItems不生效
        comboBoxHandler.MaxDropDownItems = 10;
        comboBoxHandler.DropDownStyle = ComboBoxStyle.DropDown;
        comboBoxHandler.AutoCompleteSource = AutoCompleteSource.ListItems;
        comboBoxHandler.AutoCompleteMode = AutoCompleteMode.SuggestAppend;

        comboBoxHandler.KeyPress += ComboBox_KeyPress;
        comboBoxHandler.KeyDown += ComboBox_KeyDown; // 新增绑定
        comboBoxHandler.LostFocus += Combo_LostFocus;
    }
}

2. 编辑时获取不到修改后的值？ #

因为编辑过程中CurrentCell.Value存的是原始值，实时输入的内容在ComboBox的Text属性里。要获取最新内容，得判断当前是否在编辑模式：

// 获取当前单元格的实际内容
string GetCurrentCellContent()
{
    if (dgvCustom.IsCurrentCellInEditMode && comboBoxHandler != null)
    {
        return comboBoxHandler.Text.Trim();
    }
    else
    {
        return dgvCustom.CurrentCell.Value?.ToString().Trim() ?? string.Empty;
    }
}

如果要确保编辑结束后单元格值同步，加个CellEndEdit事件：

private void dgvCustom_CellEndEdit(object sender, DataGridViewCellEventArgs e)
{
    if (comboBoxHandler != null)
    {
        dgvCustom.CurrentCell.Value = comboBoxHandler.Text.Trim();
        comboBoxHandler = null;
    }
}

内容的提问来源于stack exchange，提问作者Hellboy.