出現滾動條時如何正確應用修改后的C#WinFormListBox邊框顏色

我被要求對 C# WinForms 應用程式進行一些現代化作業，我正在使用 VS2019 和 C#.Net 4.7.2。

專案所有者想要更改最初使用的所有舊版 Windows 控制元件的邊框顏色。最初的想法是 - 使用 MetroIT 框架 - 將原始 Windows 控制元件保留在表單設計器中，但通過定義擴展 MetroIT 等效項的新類來覆寫它們，但更改設計器的 InitializeComponent() 方法中宣告的型別別。

這種方法并不能真正用作“插入式”替代品，因為 MetroIT 控制元件傾向于子類化 Control，而現有代碼希望舊版 Windows 屬性/方法可用。

相反，因此，我走上了試圖覆寫 OnPaint 方法的路線。這對于 CheckBox 和 RadioButton 來說效果很好，但我現在正在努力讓它為 ListBox 作業。以下是我所知道的；正如我將解釋的那樣，這當然不正確，但感覺有點接近？

public class MyListBox : ListBox
{
    public MyListBox()
    {
        SetStyle(ControlStyles.UserPaint, true);
        this.DrawMode = DrawMode.OwnerDrawVariable;
        BorderStyle = BorderStyle.None;
    }
    
    protected override void OnPaint(PaintEventArgs e)
    {
        base.OnPaint(e);

        Brush textBrush = new SolidBrush(Color.Black);
        float y = 1;
        foreach (String strItem in Items)
        {
            e.Graphics.DrawString(strItem, DefaultFont, textBrush, 1, y);
            y  = DefaultFont.Height;
        }

        Rectangle borderRectangle = this.ClientRectangle;
        ControlPaint.DrawBorder(e.Graphics, borderRectangle, Color.Blue, ButtonBorderStyle.Solid);
    }
}

最初，在 ListBox 中沒有資料的情況下，控制元件被正確繪制。

但是，一旦出現滾動條，基本的 Windows 代碼就會將滾動條繪制在我的邊框頂部而不是僅僅在其內部（而未修改的 ListBox 會重新繪制邊框頂部、底部和右側的邊框）滾動條）：

有沒有辦法更改我的代碼，以便邊框圍繞滾動條的邊緣繪制而不是排除它？

The other way in which my code is wrong is that, as soon as I start to scroll, the border painting code is applying itself to some of the ListBox items:

Is there a way I can complete this, or am I wasting my time because the base scroll bar cannot be modified ?

Thanks

EDIT 1:

Further to the suggestions of @GuidoG:

Yes, to be clear, I really only want to change the border to blue. Happy to leave the listbox items as they would ordinarily be painted WITHOUT any border.

So, to achieve that, I have removed your suggested code to do DrawItem, and now I only have the code to paint the border - but clearly I must be doing something wrong, because the listbox has now reverted to looking like the standard one with the black border.

So here's what I have now:

In my Dialog.Designer.cs InitializeComponent():

    this.FieldsListBox = new System.Windows.Forms.ListBox();
    this.FieldsListBox.FormattingEnabled = true;
    this.FieldsListBox.Location = new System.Drawing.Point(7, 98);
    this.FieldsListBox.Name = "FieldsListBox";
    this.FieldsListBox.Size = new System.Drawing.Size(188, 121);
    this.FieldsListBox.Sorted = true;
    this.FieldsListBox.TabIndex = 11;
    this.FieldsListBox.SelectedIndexChanged  = new System.EventHandler(this.FieldsListBox_SelectedIndexChanged);

In my Dialog.cs Form declaration:

public SelectByAttributesDialog()
{
    InitializeComponent();
    BlueThemAll(this);
}

private void BlueThemAll(Control parent)
{
    foreach (Control item in parent.Controls)
    {
        Blue(item);

        if (item.HasChildren)
            BlueThemAll(item);
    }
}

private void Blue(Control control)
{
    Debug.WriteLine("Blue: "   control.Name.ToString());
    Rectangle r = new Rectangle(control.Left - 1, control.Top - 1, control.Width   1, control.Height   1);

    using (Graphics g = control.Parent.CreateGraphics())
    {
        using (Pen selPen = new Pen(Color.Blue))
        {
            g.DrawRectangle(selPen, r);
        }
    }
}

I know that Blue() is being called for all the controls in this dialog, in the sense that the Debug.WriteLine() is outputting every control name, but no borders are being changed to blue (and certainly not the listbox).

I've been away from Windows Form programming for a very long time so I apologise for that, and I'm clearly doing something wrong, but have no idea what.

uj5u.com熱心網友回復：

解決方案 1：讓表單圍繞所有內容繪制藍色邊框：

這意味著您不必對任何控制元件進行子類化，而是在表單上放置一些代碼，這些代碼將為您在每個控制元件周圍繪制邊框。
這是一個對我有用的例子

// method that draws a blue border around a control
private void Blue(Control control)
{
    Rectangle r = new Rectangle(control.Left - 1, control.Top - 1, control.Width   1, control.Height   1);

    using (Graphics g = control.Parent.CreateGraphics())
    {
        using (Pen selPen = new Pen(Color.Blue))
        {
            g.DrawRectangle(selPen, r);
        }
    }
}

// recursive method that finds all controls and call the method Blue on each found control
private void BlueThemAll(Control parent)
{
    foreach (Control item in parent.Controls)
    {
        Blue(item);

        if (item.HasChildren)
            BlueThemAll(item);
    }
}

在哪里呼叫這個？

    // draw the blue borders when the form is resized
    protected override void OnResize(EventArgs e)
    {
        base.OnResize(e);

        panel3.Invalidate(); // on panel3 there is a control that moves position because it is anchored to the bottom
        Update();
        BlueThemAll(this);
    }

    // draw the borders when the form is moved, this is needed when the form moved off the screen and back
    protected override void OnMove(EventArgs e)
    {
        base.OnMove(e);

        BlueThemAll(this);
    }

    // draw the borders for the first time
    protected override void OnShown(EventArgs e)
    {
        base.OnShown(e);
        BlueThemAll(this);
    }

如果您還想在串列框的每個專案周圍使用藍色邊框：

要在串列框中的每個專案周圍獲得一些邊框，請使用該DrawItem事件而不是繪制事件，也許

Solution 2: Subclassing the listbox:

If you need this in a subclassed listbox, then you can do this.
However, this will only work if the listbox has at least one pixel space left around it, because to get around the scrollbar you have to draw on the parent of the listbox, not on the listbox itself. The scrollbar will always draw itself over anything you draw there.

    public class myListBox : ListBox
    {
        public myListBox(): base()
        {
            this.DrawMode = DrawMode.OwnerDrawFixed;
            BorderStyle = BorderStyle.None;
            this.DrawItem  = MyListBox_DrawItem;
        }

        private void MyListBox_DrawItem(object sender, DrawItemEventArgs e)
        {
            e.DrawBackground();
            Brush myBrush = new SolidBrush(e.ForeColor);
            e.Graphics.DrawString(this.Items[e.Index].ToString(), e.Font, myBrush, e.Bounds, StringFormat.GenericDefault);
            e.DrawFocusRectangle();

            Rectangle r = new Rectangle(this.Left - 1, this.Top - 1, this.Width   2, this.Height   2);
            using (Graphics g = this.Parent.CreateGraphics())
            {
                ControlPaint.DrawBorder(g, r, Color.Blue, ButtonBorderStyle.Solid);
            }
        }
    }

and this will look like so

標籤：c# winforms

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