每次构建后更改自定义ListView.Items

Question

我创建了一个自定义的ListView，该ListView继承自.NET中的标准enum，以显示Items WinForms个public class ScrapGroupsListView : ListView { public event EventHandler SelectedColorChanged; private ScrapGroup _selectedGroup = ScrapGroup.None; [DefaultValue(ScrapGroup.None)] public ScrapGroup SelectedScrapGroup { get { return _selectedGroup; } set { if (_selectedGroup != value) { _selectedGroup = value; foreach (ListViewItem item in this.Items) { if (item != null) { if (item.Tag != null) { var itemColor = (ScrapGroup)item.Tag; if (itemColor == ScrapGroup.None) item.Checked = value == ScrapGroup.None; else item.Checked = value.HasFlag(itemColor); } } } if (SelectedColorChanged != null) SelectedColorChanged.Invoke(this, EventArgs.Empty); } } } public ScrapGroupsListView() { this.Items.Clear(); this.CheckBoxes = true; this.HeaderStyle = ColumnHeaderStyle.None; this.View = View.List; foreach (var value in Enum.GetValues(typeof(ScrapGroup)).Cast<ScrapGroup>()) { this.Items.Add(new ListViewItem() { Name = value.ToString(), Text = value.ToString(), Tag = value, }); } } protected override void OnItemChecked(ItemCheckedEventArgs e) { base.OnItemChecked(e); var checkedScrapGroup = (ScrapGroup)e.Item.Tag; if (e.Item.Checked) if (checkedScrapGroup == ScrapGroup.None) SelectedScrapGroup = ScrapGroup.None; else SelectedScrapGroup |= checkedScrapGroup; else SelectedScrapGroup &= ~checkedScrapGroup; } } 项目）：

ScrapGrouop

[Flags] public enum ScrapGroup { None=0, M=1, E=2, N=4, H=8 } 是我的枚举：

ScrapGroupsListView

当我将ScrapGroup放到我的表单中时，一切正常，控件没有项目：

但每次构建项目时，ScrapGroupsListView.Items值都会添加到Utilities.getBaseURL()（设计时）：

第一次构建后

：

第二次构建后

：

等等。

问题出在哪里？

Answer 1

而不是构造函数试试：

protected override void OnCreateControl()
    {
        base.OnCreateControl();

        this.Items.Clear();
        this.CheckBoxes = true;
        this.HeaderStyle = ColumnHeaderStyle.None;
        this.View = View.List;

        foreach (var value in Enum.GetValues(typeof(ScrapGroup)).Cast<ScrapGroup>())
        {
            this.Items.Add(new ListViewItem()
            {
                Name = value.ToString(),
                Text = value.ToString(),
                Tag = value,
            });
        }
    }

Answer 2

每次在VS设计器中打开表单时，都会创建以下代码：

private void InitializeComponent()
{
    System.Windows.Forms.ListViewItem listViewItem1 = new System.Windows.Forms.ListViewItem("None");
    System.Windows.Forms.ListViewItem listViewItem2 = new System.Windows.Forms.ListViewItem("M");
    System.Windows.Forms.ListViewItem listViewItem3 = new System.Windows.Forms.ListViewItem("E");
    System.Windows.Forms.ListViewItem listViewItem4 = new System.Windows.Forms.ListViewItem("N");
    System.Windows.Forms.ListViewItem listViewItem5 = new System.Windows.Forms.ListViewItem("H");
    this.scrapGroupsListView1 = new ScrapGroupsListView();
    // 
    // scrapGroupsListView1
    // 
    this.scrapGroupsListView1.CheckBoxes = true;
    this.scrapGroupsListView1.HeaderStyle = System.Windows.Forms.ColumnHeaderStyle.None;
    listViewItem1.StateImageIndex = 0;
    listViewItem1.Tag = ScrapGroup.None;
    listViewItem2.StateImageIndex = 0;
    listViewItem2.Tag = ScrapGroup.M;
    listViewItem3.StateImageIndex = 0;
    listViewItem3.Tag = ScrapGroup.E;
    listViewItem4.StateImageIndex = 0;
    listViewItem4.Tag = ScrapGroup.N;
    listViewItem5.StateImageIndex = 0;
    listViewItem5.Tag = ScrapGroup.H;
    this.scrapGroupsListView1.Items.AddRange(new System.Windows.Forms.ListViewItem[] {
    listViewItem1,
    listViewItem2,
    listViewItem3,
    listViewItem4,
    listViewItem5});

这就是您的商品出现两次的原因。首先从构造函数设置，第二组来自InitializeComponent()。

您可以（并且应该）从InitializeComponent()删除代码，但在设计器中打开表单会再次搞砸。

为了防止这种情况，您可以将填充代码移动到单独的方法并从表单中调用它。

在你的控制中：

public ScrapGroupsListView()
{
    this.CheckBoxes = true;
    this.HeaderStyle = ColumnHeaderStyle.None;
    this.View = View.List;
}

public void Fill()
{
    this.Items.Clear();

    foreach( var value in Enum.GetValues( typeof( ScrapGroup ) ).Cast<ScrapGroup>() )
    {
        this.Items.Add( new ListViewItem()
        {
            Name = value.ToString(),
            Text = value.ToString(),
            Tag = value,
        } );
    }
}

以您的形式：

public MainForm()
{
    InitializeComponent();

    scrapGroupsListView1.Fill();
}

作为此解决方案的缺点，您无法在设计师中看到您的商品。