以编程方式在 Asp.Net ListView 中选择项目 [英] Programmatically Select Item in Asp.Net ListView

问题描述

在快速搜索之后，我找不到这个看似简单的事情的答案.

After doing a quick search I can't find the answer to this seemingly simple thing to do.

如何在 Asp.Net ListView 中手动选择项目?

我有一个 SelectedItemTemplate，但我不想使用 asp:button 或 asp:LinkBut​​ton 来选择项目.我希望它是从一个 URL 完成的.例如，像 QueryString.

I have a SelectedItemTemplate, but I don't want to use an asp:button or asp:LinkButton to select an item. I want it to be done from a URL. Like a QueryString, for example.

我想象的方式是在 ItemDataBound 上，检查一个条件，然后将其设置为 selected(如果为真)，但我该怎么做?

The way I imagine would be on ItemDataBound, check a condition and then set it to selected if true, but how do I do this?

例如:

protected void lv_ItemDataBound(object sender, ListViewItemEventArgs e) {

  using (ListViewDataItem dataItem = (ListViewDataItem)e.Item) {

     if (dataItem != null) {
        if( /* item select condition */ ) {   

            // What do I do here to Set this Item to be Selected?
            // edit: Here's the solution I'm using :
            ((ListView)sender).SelectedIndex = dataItem.DisplayIndex;

            // Note, I get here and it gets set
            // but the SelectedItemTemplate isn't applied!!!

        }
     }
  }
}

我确定这是一两行代码.

I'm sure it's one or two lines of code.

我已经更新了代码以反映解决方案，似乎我可以选择 ListView 的 SelectedItemIndex，但是，它实际上并没有呈现 SelectedItemTemplate.我不知道我是否应该按照下面的建议在 ItemDataBound 事件中执行此操作.

I've updated the code to reflect the solution, and it seems that I can select the ListView's SelectedItemIndex, however, it's not actually rendering the SelectedItemTemplate. I don't know if I should be doing this in the ItemDataBound event as suggested below.

推荐答案

我查看了 ListView 内部发生的一些事情，并认为这可能是最好的方法.

I looked at some of what's going on in ListView under the hood and think this is probably the best approach.

void listView_ItemCreated(object sender, ListViewItemEventArgs e)
{
    // exit if we have already selected an item; This is mainly helpful for
    // postbacks, and will also serve to stop processing once we've found our
    // key; Optionally we could remove the ItemCreated event from the ListView 
    // here instead of just returning.
    if ( listView.SelectedIndex > -1 ) return; 

    ListViewDataItem item = e.Item as ListViewDataItem;
    // check to see if the item is the one we want to select (arbitrary) just return true if you want it selected
    if (DoSelectDataItem(item)==true)
    {
        // setting the SelectedIndex is all we really need to do unless 
        // we want to change the template the item will use to render;
        listView.SelectedIndex = item.DisplayIndex;
        if ( listView.SelectedItemTemplate != null )
        {
            // Unfortunately ListView has already a selected a template to use;
            // so clear that out
            e.Item.Controls.Clear();
            // intantiate the SelectedItemTemplate in our item;
            // ListView will DataBind it for us later after ItemCreated has finished!
            listView.SelectedItemTemplate.InstantiateIn(e.Item);
        }
    }
}

bool DoSelectDataItem(ListViewDataItem item)
{
    return item.DisplayIndex == 0; // selects the first item in the list (this is just an example after all; keeping it simple :D )
}

注意事项

• ListView 选择项目在触发 DataBinding 事件后将使用的模板.所以如果在此之前设置了 SelectedIndex ，则不需要更多的工作
• 在 DataBinding 工作后的任何位置设置 SelectedIndex，您只是不会获得 SelectedItemTemplate.为此，您要么重新绑定数据；或重新实例化 ListViewItem 上的 SelectedItemTemplate.请务必先清除 ListViewItem.Controls 集合！

更新我已经删除了我的大部分原始解决方案，因为这应该会更好地适用于更多情况.

UPDATE I have removed most of my original solution, since this should work better and for more cases.

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