c# - 为什么自动选择列表框的最后一项？

Question

当我使用此规则在列表框中打开或打开多个文件时

然后自动选择列表框的最后一项。

按照我的代码:

Xaml:

<ListBox x:Name="listbox4" Background="Salmon"   BorderBrush="Black" BorderThickness="3" Drop="listbox4_Drop"  >
</ListBox>

Xaml.cs:

private Dictionary<string, string> fileDictionary = new Dictionary<string, string>();   

private void load_Click(object sender, RoutedEventArgs e)
{
    Microsoft.Win32.OpenFileDialog ofd = new Microsoft.Win32.OpenFileDialog();
    ofd.DefaultExt = ".mp3";
    ofd.Filter = "All|*.*";
    ofd.Multiselect = true;
    Nullable<bool> result = ofd.ShowDialog();
    if (result == true)
    {

        for (int i = 0; i < ofd.FileNames.Length; i++)
        {
            var filePath = ofd.FileNames[i];
            var fileName = System.IO.Path.GetFileName(filePath);
            fileDictionary.Add(fileName, filePath);
            listbox4.Items.Add(fileName);
            listbox4.SelectedItem = fileName;
        }
    }
}

    private void listbox4_Drop(object sender, DragEventArgs e)
    {
        if (e.Data.GetDataPresent(DataFormats.FileDrop))
        {

            string[] droppedFilePaths =
                e.Data.GetData(DataFormats.FileDrop, true) as string[];

            foreach (string droppedFilePath in droppedFilePaths)
            {
                var filePath = droppedFilePath;
                var fileName = System.IO.Path.GetFileName(filePath);
                fileDictionary.Add(fileName, filePath);
                listbox4.Items.Add(fileName);
                listbox4.SelectedItem = fileName;
            }

        }
    }

但我想在加载或删除时自动选择加载的第一个项目。

注意:我说的不是喜欢

listbox4.SelectedIndex=0;

我说的是在加载或删除多个文件之间选择第一项。

这怎么可能？

Answer 1

要设置您必须在加载或删除之前获取列表中的项目总数，然后在添加文件之后，将 SelectedIndex 设置为下一个值。所以你的代码看起来像这样:

private void load_Click(object sender, RoutedEventArgs e)
{
    var listCount = listbox4.Count;
    Microsoft.Win32.OpenFileDialog ofd = new Microsoft.Win32.OpenFileDialog();
    ofd.DefaultExt = ".mp3";
    ofd.Filter = "All|*.*";
    ofd.Multiselect = true;
    Nullable<bool> result = ofd.ShowDialog();
    if (result == true)
    {       
        for (int i = 0; i < ofd.FileNames.Length; i++)
        {
            var filePath = ofd.FileNames[i];
            var fileName = System.IO.Path.GetFileName(filePath);
            fileDictionary.Add(fileName, filePath);
            listbox4.Items.Add(fileName);
        }
        listbox4.SelectedIndex = listCount;
    }
}

private void listbox4_Drop(object sender, DragEventArgs e)
{
    if (e.Data.GetDataPresent(DataFormats.FileDrop))
    {
        var listCount = listbox4.Count;
        string[] droppedFilePaths =
            e.Data.GetData(DataFormats.FileDrop, true) as string[];
        foreach (string droppedFilePath in droppedFilePaths)
        {
            var filePath = droppedFilePath;
            var fileName = System.IO.Path.GetFileName(filePath);
            fileDictionary.Add(fileName, filePath);
            listbox4.Items.Add(fileName);
        }
        if(droppedFilePaths.Any())
        {
            listbox4.SelectedIndex = listCount;
        }
    }
}