如何更新ListView的选定项目? [英] How to update ListView's selected item?

问题描述

我有一个ListView，它显示ListViewItems的多行.用户可以通过单击编辑"后打开的对话框来编辑这些项目之一.对话框关闭时，我想修改所选的ListViewItem，以使其反映新的设置.

I have a ListView which displays multiple rows of ListViewItems. The user is able to edit one of these items through a dialog which opens after clicking 'Edit.' When the dialog closes I would like to modify the selected ListViewItem such that it reflects the new settings.

这是我当前更新商品的方式:

Here is how I currently update my item:

private void btnEditSnmpV3Setting_Click(object sender, EventArgs e)
{
    if (lstVwSNMPv3Settings.SelectedItems.Count > 0)
    {
        ListViewItem selectedItem = lstVwSNMPv3Settings.SelectedItems[0];
        NetworkDiscoverySnmpSetting settings = (NetworkDiscoverySnmpSetting)selectedItem.Tag;
        NetworkDiscoverySnmpV3SettingsDialog dialog = new NetworkDiscoverySnmpV3SettingsDialog(settings);

        //Pass in the owner for centering of dialog.
        if (dialog.ShowDialog(this) == DialogResult.OK)
        {
            selectedItem.SubItems.Clear();
            selectedItem.Text = settings.SnmpV3Username;
            selectedItem.SubItems.Add(settings.SecurityMode.ToString());
            selectedItem.SubItems.Add(settings.AuthenticationProtocol.ToString());
            selectedItem.SubItems.Add(settings.PrivacyProtocol.ToString());
            selectedItem.Tag = settings;
        }
    }
}

我发现这是一个较差的解决方案，因为如果ListView的列数发生变化，我需要在多个位置触摸代码.

I found this to be a poor solution due to the fact that I need to touch code in multiple places if my ListView's number of columns changes.

我通过给NetworkDiscoverySnmpSetting一个实用程序方法来处理了'Add'事件(而不是'Edit')中的代码重用问题:

I handled this code-reuse issue during the 'Add' event (as opposed to 'Edit') by giving NetworkDiscoverySnmpSetting a utility method:

public ListViewItem ToListViewItem()
{
    ListViewItem listViewItem = new ListViewItem();
    listViewItem.Text = SnmpV3Username;
    listViewItem.SubItems.Add(SecurityMode.ToString());
    listViewItem.SubItems.Add(AuthenticationProtocol.ToString());
    listViewItem.SubItems.Add(PrivacyProtocol.ToString());
    listViewItem.Tag = this;
    return listViewItem;
}

其用法如下:

private void btnAddSnmpV3Setting_Click(object sender, EventArgs e)
{
    NetworkDiscoverySnmpSetting settings = new NetworkDiscoverySnmpSetting(NetworkDiscovery.ID);
    NetworkDiscoverySnmpV3SettingsDialog dialog = new NetworkDiscoverySnmpV3SettingsDialog(settings);
    //Pass in the owner for centering of dialog.
    if (dialog.ShowDialog(this) == DialogResult.OK)
        lstVwSNMPv3Settings.Items.Add(settings.ToListViewItem());
}

不幸的是，ListView.SelectedItems不允许进行集合修改.因此，它不会编译:

Unfortunately, ListView.SelectedItems does not allow collection-modification. As such, this does not compile:

lstVwSNMPv3Settings.SelectedItems[0] = settings.ToListViewItem();

我应该如何更改第一个代码段，以便在ListView的列更改时无需在多个位置更新代码?

How should I change my first code-snippet so that I do not need to update my code in multiple places when ListView's columns change?

推荐答案

您可以修改元素本身，而不必用另一个元素替换它，因为ListViewItem是一个类，因此它是一种引用类型.

You can modify the element itself rather than replacing it with another one, because ListViewItem is a class, so it's a reference type.

为此，请按照以下步骤操作:

In order to do this follow these steps:

• 获取当前选定的项目并将其保存到变量中，如下所示:ListViewItem selectedItem = lstVwSNMPv3Settings.SelectedItems[0];

• 将您的ToListViewItem方法修改为void ToListViewItem(ListViewItem listViewItem)(返回void并以ListViewItem对象作为参数并对其进行修改，而不是创建新对象.它还应该修改现有子项目的属性，而不是创建新子项目. .它看起来或多或少是这样的:

• get currently selected item and save it to variable like this: ListViewItem selectedItem = lstVwSNMPv3Settings.SelectedItems[0];

• modify your ToListViewItem method to void ToListViewItem(ListViewItem listViewItem) (return void and take ListViewItem object as parameter and modify it instead of creating a new object. It should also rather modify properties of existing subitems than creating new ones. It can look more or less like this:

public void ToListViewItem(ListViewItem listViewItem)
{
    listViewItem.Text = SnmpV3Username;
    listViewItem.SubItems[0].Text = SecurityMode.ToString();
    listViewItem.SubItems[1].Text = AuthenticationProtocol.ToString();
    listViewItem.SubItems[2].Text = PrivacyProtocol.ToString();
    listViewItem.Tag = this;
}

致电ToListViewItem(selectedItem);

我做了一个快速测试，该方法似乎可以毫无问题地修改现有项目的文本.

I did a quick test and the method seems to modify texts of existing items without issues.

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