C# ListBox 已设置数据源但刷新什么也不做
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ListBox has set datasource but Refresh does nothing
提问by S1r-Lanzelot
I seem to be misunderstanding the ListBox.Refresh() method and I was hoping someone could help me out.
我似乎误解了 ListBox.Refresh() 方法，我希望有人可以帮助我。
What I am trying to do:
I want to load a listbox's data (source = table of a sql database) upon initialization of a windows form. Also when the user adds data to the database I would like the listbox to update.
我想要做什么：
我想在 Windows 窗体初始化时加载列表框的数据（源 = sql 数据库的表）。此外，当用户将数据添加到数据库时，我希望列表框更新。
Logic:
I have a sql database as my source, it is set as:
逻辑：
我有一个 sql 数据库作为我的源，它被设置为：
listBoxDays.DataSource = DBQuery.informationRetreval().DefaultView;
DBquery.informationRetreval() is a static method within the my DBQuery static class. All it does is set up a table from the database and then returns the table.
DBquery.informationRetreval() 是我的 DBQuery 静态类中的一个静态方法。它所做的只是从数据库中设置一个表，然后返回该表。
I set the datasource within the same method as the initializeComponent (so my listbox will load with the existing data):
我在与 initializeComponent 相同的方法中设置数据源（因此我的列表框将加载现有数据）：
public Settings()
{
InitializeComponent();
listBoxDays.DataSource = DBQuery.informationRetreval().DefaultView;
}
When the user adds more data: I call a method in which I add the data to the database and then I call:
当用户添加更多数据时：我调用一个方法，将数据添加到数据库中，然后调用：
listBoxDays.Refresh(); //update listbox
The Problem: This does not update the listbox. Upon initialization of my listbox the data will populate but after it will not change (hence refresh does not work). Why is that? I could set the DataSource again but that feels sloppy. After looking into some of the documentation I noticed the event handler DataSourceChanged which maybe more for what I am looking for. Nevertheless why wouldn't refresh work?
问题：这不会更新列表框。在我的列表框初始化时，数据将填充，但之后不会改变（因此刷新不起作用）。这是为什么？我可以再次设置数据源，但这感觉很草率。在查看了一些文档后，我注意到事件处理程序 DataSourceChanged 可能更适合我正在寻找的内容。然而为什么不能刷新工作？
Thank you for your patience. Please let me know if I need to be more clear.
感谢您的耐心等待。如果我需要更清楚，请告诉我。
采纳答案by Hanlet Esca?o
Refresh(): Forces the control to invalidate its client area and immediately redraw itself and any child controls.
Refresh()：强制控件使其客户区无效并立即重绘自身和任何子控件。
Refresh will not rebind your control, it will just cause the control to be redrawn. You will have to set the DataSourceagain with
刷新不会重新绑定您的控件，它只会导致重新绘制控件。你将不得不DataSource再次设置
listBoxDays.DataSource = DBQuery.informationRetreval().DefaultView;
and re-bind it.
并重新绑定。
Source: Microsoft MSDN
来源：微软 MSDN
回答by RandomUs1r
It'll only refresh when objects have changed (ex. a different query), not the data. You can do this:
它只会在对象发生变化（例如不同的查询）时刷新，而不是数据。你可以这样做：
listBoxDays.DataSource = null;
listBoxDays.DataSource = DBQuery.informationRetreval().DefaultView;
to refresh it... everytime you need to.
刷新它...每次你需要。
