Question

我有一个datagridview，我有一些代码可以查看某些下拉列表是否已被更改。

        private void tbl_TransactionsDataGridView_EditingControlShowing(object sender, DataGridViewEditingControlShowingEventArgs e)
    {
        ComboBox combo = e.Control as ComboBox;
        if (combo != null && tbl_TransactionsDataGridView.CurrentCell.ColumnIndex == 3)
        {
            // Remove an existing event-handler, if present, to avoid  
            // adding multiple handlers when the editing control is reused.
            combo.SelectedIndexChanged -=
                new EventHandler(ComboBox_SelectedIndexChanged);

            // Add the event handler. 
            combo.SelectedIndexChanged +=
                new EventHandler(ComboBox_SelectedIndexChanged);
        }

        if (combo != null && tbl_TransactionsDataGridView.CurrentCell.ColumnIndex == 6)
        {
            // Remove an existing event-handler, if present, to avoid  
            // adding multiple handlers when the editing control is reused.
            combo.SelectedIndexChanged -=
                new EventHandler(Status_SelectedIndexChanged);

            // Add the event handler. 
            combo.SelectedIndexChanged +=
                new EventHandler(Status_SelectedIndexChanged);
        }
    }

当ColumnIndex为6时，它会跳转到以下代码。令人抓狂的是，这适用于我从下拉列表中选择的任何值，除了1.如果我选择1，我会得到一个InvalidCastException，告诉我需要使用小于无穷大的数字。如果我选择任何其他数字，一切都会按照预期发射。我做错了什么？

        private void Status_SelectedIndexChanged(object sender, EventArgs e)
    {
        object oStatus = new object();
        oStatus = ((ComboBox)sender).SelectedValue;

        if (!Convert.IsDBNull(oStatus))
        {
            SendKeys.Send("{TAB}");
            if (Convert.ToInt32(oStatus) != 1)
            {
                tbl_TransactionsDataGridView.CurrentRow.Cells["CheckInEmployee"].Value = Environment.UserName;
                tbl_TransactionsDataGridView.CurrentRow.Cells["CloseDate"].Value = DateTime.Now;
            }

            if (Convert.ToInt32(oStatus) == 1)
            {
                tbl_TransactionsDataGridView.CurrentRow.Cells["CheckOutEmployee"].Value = Environment.UserName;
                tbl_TransactionsDataGridView.CurrentRow.Cells["CheckInEmployee"].Value = null;
                tbl_TransactionsDataGridView.CurrentRow.Cells["CloseDate"].Value = null;
            }
        }
    }

Answer 1

您的意思是使用ComboBox.SelectedValue吗？这涉及数据绑定，我不能告诉你绑定的内容。

如果您只是将int添加到ComboBox.Items集合中，请使用SelectedItem。此属性也可以返回null ...请注意，null输入Convert.IsDBNull会返回false。请参阅here。

最后，将Convert投射到Int32，如此：

private void Status_SelectedIndexChanged(object sender, EventArgs e)
{
    object oStatus = new object();
    oStatus = ((ComboBox)sender).SelectedItem;

    if (oStatus != null && !Convert.IsDBNull(oStatus))
    {
        SendKeys.Send("{TAB}");
        if (((int)oStatus) != 1)
        {
            tbl_TransactionsDataGridView.CurrentRow.Cells["CheckInEmployee"].Value = Environment.UserName;
            tbl_TransactionsDataGridView.CurrentRow.Cells["CloseDate"].Value = DateTime.Now;
        }
        else
        {
            tbl_TransactionsDataGridView.CurrentRow.Cells["CheckOutEmployee"].Value = Environment.UserName;
            tbl_TransactionsDataGridView.CurrentRow.Cells["CheckInEmployee"].Value = null;
            tbl_TransactionsDataGridView.CurrentRow.Cells["CloseDate"].Value = null;
        }
    }
}

或者就此而言，您可以使用ComboBox.SelectedIndex代替。

C＃InvalidCastException仅适用于一个值？

1 个答案: