SfDataGrid如何获取选中行数及右键菜单点击时判断选中行

一、检查是否有行被选中 #

在MenuFlyoutItem_Clicked方法开头，通过以下两种方式判断是否存在选中行（任选其一即可，推荐结合使用）：

• 检查当前激活行是否为空：if (PasswdVw.CurrentRow == null)
• 检查选中行集合的数量：if (PasswdVw.SelectedItems.Count == 0)

二、获取选中行数 #

直接通过SfDataGrid的SelectedItems.Count属性获取选中行数，无选中行时返回0，有选中行时返回对应数量：

int selectedRowCount = PasswdVw.SelectedItems.Count;

三、修改后的MenuFlyoutItem_Clicked事件代码 #

在代码开头加入判断逻辑，避免空引用崩溃，同时优化重复类型转换操作：

private void MenuFlyoutItem_Clicked(object sender, EventArgs e)
{
    // 无选中行时直接返回，避免后续操作崩溃
    if (PasswdVw.CurrentRow == null || PasswdVw.SelectedItems.Count == 0)
    {
        // 可选：添加用户提示，比如MessageBox.Show("请先选择一行数据");
        return;
    }

    MenuFlyoutItem mnuItem = sender as MenuFlyoutItem;
    string takeAct = mnuItem.CommandParameter as string;
    PasswrdInfo selectedRow = PasswdVw.CurrentRow as PasswrdInfo;
    string url = selectedRow.PassUrl;
    
    string msg, retVal;
    msg = retVal = "";
    int idno = selectedRow.PassId;

    switch (takeAct)
    {
        case "UsrName":
            using (SqlConnection c = new SqlConnection(App.ConnStr))
            {
                string query = "select usrname from PassWrds where Id = " + idno;
                using (SqlCommand cmd = new SqlCommand(query, c))
                {
                    c.Open();
                    var queryResult = cmd.ExecuteScalar();
                    retVal = queryResult?.ToString() ?? "";
                    c.Close();

                    if (!string.IsNullOrEmpty(retVal))
                    {
                        Clipboard.SetTextAsync(retVal);
                        msg = "User Name copied.";
                    }
                }
            }
            break;
        case "Passwd":
            using (SqlConnection c = new SqlConnection(App.ConnStr))
            {
                string query = "select password from PassWrds where Id = " + idno;
                using (SqlCommand cmd = new SqlCommand(query, c))
                {
                    c.Open();
                    var queryResult = cmd.ExecuteScalar();
                    retVal = queryResult?.ToString() ?? "";
                    c.Close();
                }

                if (!string.IsNullOrEmpty(retVal))
                {
                    string decryptedResult = Crypto.Decrypt(App.secretKey, retVal);
                    Clipboard.SetTextAsync(decryptedResult);
                    msg = "Password copied.";
                }
            }
            break;
        case "WebSite":
            //Nothing Yet.
            break;
    }
}

额外优化：对数据库查询结果做null判断，避免查询为空时触发ToString()空引用异常。

四、进阶优化：上下文菜单显示前禁用无效项 #

可以在菜单打开前自动禁用菜单项，从源头避免无效操作：

1. 给MenuFlyout添加Opening事件
2. 在事件中根据选中行数量控制菜单项启用状态：

private void MenuFlyout_Opening(object sender, object e)
{
    bool hasSelectedRow = PasswdVw.SelectedItems.Count > 0;
    MenuFlyout flyout = sender as MenuFlyout;
    foreach (var item in flyout.Items)
    {
        if (item is MenuFlyoutItem menuItem)
        {
            menuItem.IsEnabled = hasSelectedRow;
        }
    }
}

3. 绑定到XAML的MenuFlyout上：

<FlyoutBase.ContextFlyout>
    <MenuFlyout Opening="MenuFlyout_Opening">
        <MenuFlyoutItem Text="Copy User Name"
                        Clicked="MenuFlyoutItem_Clicked"
                        CommandParameter="UsrName"/>
        <MenuFlyoutItem Text="Copy Password"
                        Clicked="MenuFlyoutItem_Clicked"
                        CommandParameter="Passwd"/>
        <MenuFlyoutItem Text="Copy Web Site"
                        Clicked="MenuFlyoutItem_Clicked"
                        CommandParameter="WebSite"/>
    </MenuFlyout>
</FlyoutBase.ContextFlyout>

内容的提问来源于stack exchange，提问作者user21591607