CheckBoxList 中的“全选”

Question

我有一些工作代码，但我认为这不是实现目标的最佳方式。

我有一个包含 5 个项目的 CheckBoxList - 4 个单独的项目和 1 个“全选”项目。选择完全选择时，我希望其他4要为用户签出。当 Select All 被取消选择时，我希望其他 4 个为用户取消选中。

我在 StackOverflow 和 Google 上发现的一堆东西只是建议遍历 CheckBoxList.Items，但这不适用于我的情况。例如，假设用户未选中 Item #3 - 这将触发 OnSelectedIndexChanged 事件，此时我将开始循环遍历 Items。我会发现未选择“全选”项目，因此我会取消选择所有项目。因此，用户会选中第 3 项，只是为了让他们立即取消选择它。

下面是我的工作代码，但它使用了一些奇怪的功能，我无法想象这是实现我正在寻找的最佳方式。

    protected void StatusCheckBoxListChanged(object sender, System.EventArgs e)
    {
        //Crazy code I found online to determine which item triggered the event
        CheckBoxList list = (CheckBoxList)sender;
        string[] control = Request.Form.Get("__EVENTTARGET").Split('$');
        int index = control.Length - 1;
        ListItem li = (ListItem)list.Items[Int32.Parse(control[index])];

        if (li.ToString().Equals("Select All")) //If it was the "Select All" Item which triggered the event
        {
            //If it was checked, check off everything. If it was unchecked, uncheck everything.
            for(int i = 0; i < StatusCheckBoxList.Items.Count; i++)
            {
                StatusCheckBoxList.Items[i].Selected = StatusCheckBoxList.Items.FindByValue("Select All").Selected;
            }
        }
    }

Answer 1

您可以尝试向您的页面添加字段，该字段显示全选的先前值，如下所示

bool SelectAll;

在PageLoad 事件处理程序中初始化它，像这样

protected void Page_Load(object sender, EventArgs e)
{
    if(!IsPostback){
        SelectAll = StatusCheckBoxList.Items.Cast<ListItem>().FirstOrDefault(d => d.Text == "Select All" && d.Selected) != null;

    }
}

并像这样更改您的活动

protected void StatusCheckBoxListChanged(object sender, System.EventArgs e)
{
    if(SelectAll != (StatusCheckBoxList.Items.Cast<ListItem>().FirstOrDefault(d => d.Text == "Select All" && d.Selected) != null)){
        SelectAll = !SelectAll;
        foreach(var li in StatusCheckBoxList.Items){
            li.Selected = SelectAll;
        }
    }
}

注意：如果您知道具有“全选”值的项目的位置，您可以在没有 LINQ 的情况下执行类似这样的操作

“全选”为第一项时的示例

protected void Page_Load(object sender, EventArgs e)
{
    if(!IsPostback){
        SelectAll = StatusCheckBoxList.Items[0].Selected;
        foreach(var li in StatusCheckBoxList.Items){
            li.Selected = SelectAll;
        }
    }
}

并像这样更改您的活动

protected void StatusCheckBoxListChanged(object sender, System.EventArgs e)
{
    if(SelectAll != StatusCheckBoxList.Items[0].Selected){
        SelectAll = !SelectAll;
        foreach(var li in StatusCheckBoxList.Items){
            li.Selected = SelectAll;
        }
    }
}

Answer 2

我过去曾通过设置标志来解决此问题，例如

public class MyClass
{
    bool _IsReady = true;

    protected void StatusCheckBoxListChanged(object sender, System.EventArgs e)
    {
        if (!_IsReady)
        {
            return;
        }

        //Crazy code I found online to determine which item triggered the event
        CheckBoxList list = (CheckBoxList)sender;
        string[] control = Request.Form.Get("__EVENTTARGET").Split('$');
        int index = control.Length - 1;
        ListItem li = (ListItem)list.Items[Int32.Parse(control[index])];

        if (li.ToString().Equals("Select All")) //If it was the "Select All" Item which triggered the event
        {
            SetAllStatusItemsSelected(StatusCheckBoxList.Items.FindByValue("Select All").Selected);
        }
    }


    private void SetAllStatusItemsSelected(bool IsSelected)
    {
        _IsReady = false;

        //If it was checked, check off everything. If it was unchecked, uncheck everything.
        for(int i = 0; i < StatusCheckBoxList.Items.Count; i++)
        {
            StatusCheckBoxList.Items[i].Selected = StatusCheckBoxList.Items.FindByValue("Select All").Selected;
        }

        _IsReady = true;
    }

}

我很想知道是否有更优雅的方式。

Answer 3

这是我一直解决这个问题的方法

        protected void CheckBoxList1_SelectedIndexChanged(object sender, EventArgs e)
    {
        CheckBoxList lstBx = (CheckBoxList)sender;

        List<ListItem> list = lstBx.Items.Cast<ListItem>().ToList();
        string[] control = Request.Form.Get("__EVENTTARGET").Split('$');
        int index = Convert.ToInt32(control[control.Length - 1]);

        ListItem selectAllControl = list.FirstOrDefault(x => x.Text == "Select All");
        ListItem selectAll = list.FirstOrDefault(x => x.Selected && x.Text == "Select All");

        if (index == 0)
        {               
            if (selectAll != null)
            {
                foreach (var item in list)
                {
                    item.Selected = true;
                }
            }
        }
        else
        {
            if (selectAllControl != null)
            {
                selectAllControl.Selected = false;
            }
        }

    }