C# 组合框不显示项目

发布于 2024-11-27 13:53:15 字数 857 浏览 1 评论 0原文

我试图在 C# 中填充组合框，但由于某种原因，这些项目没有出现。

public List<string> items
{
    set
    {
        combobox.Items.Clear();
        foreach(string s in value)
        {
            combobox.Items.Add(s);
        }
        combobox.Update();
    }
}

这看起来是非常简单的代码。我根本看不出哪里出了问题。它是这样调用的：

private void StoreNames(List<string> names)
{
    if (selectionForm.InvokeRequired)
        selectionForm.Invoke((MethodInvoker)delegate { selectionForm.items = names; });
    else
        selectionForm.items = names;
}

有趣的是，当 InvokeRequired 返回 true 时它似乎可以工作，但当它返回 false 时则不起作用。

编辑：我发现 selectionForm.IsHandleCreated 当前为 false。这会导致 InvokeRequired 返回 false，但这也是定期调用 setter 不起作用的原因。我不知道为什么 IsHandleCreated 设置为 false。该表格已被 Show()n 。

原文

I am trying to populate a combobox in C#, but for some reason, the items do not appear.

public List<string> items
{
    set
    {
        combobox.Items.Clear();
        foreach(string s in value)
        {
            combobox.Items.Add(s);
        }
        combobox.Update();
    }
}

This seems like incredibly straightforward code. I simply cannot see what is wrong.
It is being called like this:

private void StoreNames(List<string> names)
{
    if (selectionForm.InvokeRequired)
        selectionForm.Invoke((MethodInvoker)delegate { selectionForm.items = names; });
    else
        selectionForm.items = names;
}

Interestingly, it seems to work when InvokeRequired returns true, but does not work when it returns false.

EDIT:
I discovered that selectionForm.IsHandleCreated is currently false. This is causing InvokeRequired to return false, but is also why calling the setter regularly isn't working. I don't have any idea why IsHandleCreated is set to false. The Form has been Show()n.

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木有鱼丸 2024-12-04 13:53:15

不知道为什么你的代码不起作用 - 我尝试过，它工作得很好。

然而，下面是一些更简单的代码，它也可以工作——你可能会发现这样做反而会让你的问题消失。这确实假设没有其他原因导致您需要遍历该属性 - 这是一种非常不寻常的做事方式。

public void StoreNames(List<string> input)
{
    if (comboBox1.InvokeRequired)
        comboBox1.Invoke((MethodInvoker)delegate {
            StoreNames(input);
        });
    else
    {
        comboBox1.Items.Clear();
        comboBox1.Items.AddRange(input.ToArray());
    }
}

在这里，我们只是将列表直接传递给组合框上的 items.AddRange() 方法。

我怀疑这对你不起作用 - 正在发生其他事情，但我已经从后台工作者（其中 InvokeRequired 为 true）和主 UI 线程尝试过它。

Not sure why your code isn't working - I tried it and it works just fine.

However, below is some more straightforward code which also works - you may find that doing it this way instead makes your problem go away. This does presume that there is not other reason why you need to go through that property - that is quite an unusual way of doing things.

public void StoreNames(List<string> input)
{
    if (comboBox1.InvokeRequired)
        comboBox1.Invoke((MethodInvoker)delegate {
            StoreNames(input);
        });
    else
    {
        comboBox1.Items.Clear();
        comboBox1.Items.AddRange(input.ToArray());
    }
}

Here we just pass the list straight to the items.AddRange() method on the comboBox.

I suspect this won't work for you - something else is going on, but I have tried it both from a backgroundworker (where InvokeRequired is true) and from the main UI thread.

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