C# 捕获异常

Question

我对此很陌生，所以请帮忙。我有以下图像点击代码。但是，如果用户没有点击图像，就会发生错误。如果用户没有点击图片并尝试继续，我该如何进行错误检查以发现消息框将显示，通知他点击图片。

错误消息:错误位于“ListViewItem selectedItem = listView1.SelectedItems[0] 错误消息:无效参数 = ‘0’的值对于‘index’无效

下面是我的代码:

private void worker_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
    int i = e.ProgressPercentage;
    object fbUserObject = e.UserState;
    if (fbUserObject is DataRow)
    {
        var fbUser = fbUserObject as DataRow;
        var item = new ListViewItem(fbUser["friend_name"].ToString());
        item.Tag = fbUser["friend_id"];
        item.ImageIndex = i;
        listView1.Items.Add(item);
    }
    else if (fbUserObject is Image)
    {
        imageList.Images.Add(fbUserObject as Image);
    }  
}

private void imageClicked(Object sender, System.EventArgs e)
{
    ListViewItem selectedItem = listView1.SelectedItems[0];
    selectedFBId = selectedItem.Tag as string;
    selectedFBName = selectedItem.Text;

    DialogResult dialogA = MessageBox.Show("Analyse employee data?", "SOC", MessageBoxButtons.YesNo);
    if (dialogA == DialogResult.Yes)
    {
        TargetEmployee.Text = "Selected Target: " + selectedFBName;
        pf.Show();
        ThreadPool.QueueUserWorkItem(LoadUserDetails);
    }
}

Answer 1

你不应该捕获异常，你应该在没有任何被选中的项目时处理

if(listView1.SelectedItems.Count == 0)
{
 MessageBox.Show(this, "No image");
return;
}

当您不希望发生某些事情时应该捕获异常，如果您知道可能的问题，您应该在它成为问题之前处理它