listBox selectedItem问题 [英] listBox selectedItem issue

问题描述

大家好.

这很好用

Hello to everybody.

This works fine

private void btnDelete_Click(object sender, EventArgs e)
{
    for (int i = 0; i < listBox1.SelectedItems.Count; i++)
    {
        listBox1.Items.Remove(listBox1.SelectedItems[i].ToString());
        i--;
    }
}

但这不起作用:

But this doesn''t work:

private void btnDelete_Click(object sender, EventArgs e)
{
    listBox1.Items.Remove(listBox1.SelectedItems);
}

为什么第二个btnDelete_Click不起作用?我的意思是我用鼠标在listBox1上选择了一行，然后按按钮. .Remove功能不能识别我选择的哪一行?即使我说.Remove(listBox1.SelectedItem)，是否必须要有一个selectedTable数组? "SelectedItems"一词不是不言自明的吗?而且由于我用鼠标单击了listBox1上的行，因此程序或IDE无法理解选择了哪一行?为什么我仍必须使用SelectedItems [i]?

Why is the second btnDelete_Click not working? I mean I select a line on my listBox1 with my mouse and then press the button. Doesn''t the .Remove function recognize which line I selected? Even though I say .Remove(listBox1.SelectedItem), is it a must to have and selectedItem array? Isn''t the word SelectedItems self-explanatory? And since I clicked the line on my listBox1 with my mouse, can''t the program or the IDE understand which line is selected? Why do I still have to use SelectedItems[i]?

推荐答案

删除"功能一次只能删除一个对象，而"SelectedItems"功能只能删除一次返回所选项目的集合(因为您可能有多个所选项目).您还可以使用以下代码:

The "Remove" function lets you only remove one object at a time, but the "SelectedItems" function returns a collection of the selected items (since you may have multiple selected items). You could also use this code:

while(listBox1.SelectedItems.Count > 0)
{
   listBox1.Items.Remove(listBox1.SelectedItem);
}

第二个btnDelete_Click为什么不起作用:

因为Remove方法期望元素被删除，但是SelectedItems属性返回项目的集合.

我的意思是我用鼠标在listBox1上选择一行，然后按按钮. .Remove功能不能识别我选择的哪一行?即使我说.Remove(listBox1.SelectedItem)，是否必须要有一个selectedTable数组?
这个词不是很明显吗?

集合的通用Remove功能与GUI状态(如选定项)有什么关系?如果您想使用删除所选内容"功能，则第一个解决方案将可以正常工作(除非您不需要ToString调用).自我解释是什么意思?对于编译器?您在这里不做魔术-它是程序设计.

由于我用鼠标单击了listBox1上的行，因此程序或IDE无法理解选择了哪一行?

这个问题给了我一个强烈的提示"，你是一个初学者……运行时没有IDE，程序"了解选择了哪些行(您可以调用SelectedItems属性来检索它们，做到了，没有."你吗?)

为什么我仍然必须使用SelectedItems [i]?
因为Remove方法要删除该对象(如docu/intellisense所述).使用Index运算符，您可以从集合中获得一个元素-要删除的元素.

结论:我承认RemoveRange方法对于列表框而言将是一个不错的功能.但是您的其他问题来自缺乏对某些基础知识的理解，似乎您对框架没有太多经验-.NET的优点是:它非常统一，如果您将它用于Items-collection，则可以理解适用于所有集合(其中一些具有RemoveRange方法)
如果您仍然不喜欢它.实现您自己的Listbox(派生)或为ListBox.ObjectCollection创建扩展方法.最后，它始终是相同的，对我来说，编程是一件好事:如果您不喜欢它的方式，请根据自己的需要创建一段代码-对于这个问题，您可以明确地做到这一点那-但是我认为您最终会坚持第一个解决方案.

Why is the second btnDelete_Click not working:

Because the Remove method expects the element to remove but the SelectedItems property returns a collection of items.

I mean I select a line on my listBox1 with my mouse and then press the button. Doesn''t the .Remove function recognize which line I selected? Even though I say .Remove(listBox1.SelectedItem), is it a must to have and selectedItem array? Isn''t the word SelectedItems self-explanatory?

What has the generic Remove function of a collection to do with a GUI state like selected items? If you want a "Remove selected" function your first solution will work fine (except you don''t need the ToString call). What you mean by self-explainatory? for the compiler? You don''t do magic here - it''s programming.

And since I clicked the line on my listBox1 with my mouse, can''t the program or the IDE understand which line is selected?

This questions gives me a "strong hint" you are a beginner... There is no IDE at runtime, the "program" understands which lines are selected (you can call the SelectedItems property to retrieve them, you did that, didn''t you?)

Why do I still have to use SelectedItems[i]?
because the Remove method want''s the object to remove (like the docu/intellisense says). And with the Index operator you get one element out of a collection - the one you want to remove.

Conclusion: I admit that a RemoveRange method would be a nice feature for a listbox. But your other questions come from a lack of understanding some basics and it seems you don''t have much experience with the framework - the good thing about .NET: it is very uniform, if you get it for the Items-collection you understand it for all collections (some of them have a RemoveRange method)
If you still don''t like it. Implement your own Listbox (derive) or create an extension method for ListBox.ObjectCollection. In the end it''s always the same, and for me a good thing about programming: If you don''t like the way it is, create your own piece of code for your needs - and for this problem you can clearly do that - but I think you will stick to your first solution in the end.

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