在Windows窗体中更改ComboBox边框颜色 [英] Change ComboBox Border Color in Windows Forms

问题描述

在我的应用程序中，我添加了组合框，如下图所示

我已将combobox属性设置为

  cmbDatefilter.FlatStyle = System.Windows.Forms.FlatStyle。平面; 
  

现在我的问题是如何将边框样式设置为组合框，以使其看起来不错。 p>

我在下面的链接中验证

 使用系统； 
使用System.Drawing; 
使用System.Windows.Forms; 
 
公共类FlatCombo：ComboBox 
 {
 private const int WM_PAINT = 0xF; 
 private int buttonWidth = SystemInformation.Horizo​​ntalScrollBarArrowWidth; 
 Color borderColor = Color.Blue; 
 public Color BorderColor 
 {
 get {return borderColor; } 
 set {borderColor = value; Invalidate（）; } 
} 
受保护的覆盖无效WndProc（ref Message m）
 {
 base.WndProc（ref m）; 
 if（m.Msg == WM_PAINT&& DropDownStyle！= ComboBoxStyle.Simple）
 {
使用（var g = Graphics.FromHwnd（Handle））
 {
 using（var p = new Pen（BorderColor））
 {
 g.DrawRectangle（p，0，0，Width-1，Height-1）; 
 
 var d = FlatStyle == FlatStyle.Popup？ 1：0； 
 g.DrawLine（p，Width-buttonWidth-d，
 0，Width-buttonWidth-d，Height）; 
} 
} 
} 
} 
} 
  

注意：

• 在上面的示例中，我使用前景色作为边框，可以添加一个 BorderColor 属性或使用其他颜色。


• 如果您不喜欢下拉按钮的左边框，则可以将 DrawLine 方法。


• 当控件为 RightToLeft 时，您需要绘制线code>（0，buttonWidth）到（Height，buttonWidth）


• 了解更多有关如何呈现平面组合框的信息，您可以查看内部 ComboBox.FlatComboAdapter 类。

In My Application i have added Combobox as shown in below picture

i have set the combobox property as

cmbDatefilter.FlatStyle = System.Windows.Forms.FlatStyle.Flat;

And now my question is how to set border style to combobox so that it will look nice.

I verified in below link

Flat style Combo box

My question is different from below link's.

Generic ComboBox in Windows Forms Application

How to override UserControl class to draw a custom border?

解决方案

You can inherit from ComboBox and override WndProc and handle WM_PAINT message and draw border for your combo box:

using System;
using System.Drawing;
using System.Windows.Forms;

public class FlatCombo : ComboBox
{
    private const int WM_PAINT = 0xF;
    private int buttonWidth = SystemInformation.HorizontalScrollBarArrowWidth;
    Color borderColor = Color.Blue;
    public Color BorderColor
    {
        get { return borderColor; }
        set { borderColor = value; Invalidate(); }
    }
    protected override void WndProc(ref Message m)
    {
        base.WndProc(ref m);
        if (m.Msg == WM_PAINT && DropDownStyle != ComboBoxStyle.Simple)
        {
            using (var g = Graphics.FromHwnd(Handle))
            {
                using (var p = new Pen(BorderColor))
                {
                    g.DrawRectangle(p, 0, 0, Width - 1, Height - 1);

                    var d = FlatStyle == FlatStyle.Popup ? 1 : 0;
                    g.DrawLine(p, Width - buttonWidth - d,
                        0, Width - buttonWidth - d, Height);
                }
            }
        }
    }
}

Note:

• In the above example I used fore color for border, you can add a BorderColor property or use another color.
• If you don't like the left border of dropdown button, you can comment that DrawLine method.
• You need to draw line when the control is RightToLeft from (0, buttonWidth) to (Height, buttonWidth)
• To learn more about how to render a flat combo box, you can take a look at source code of internal ComboBox.FlatComboAdapter class of .Net Framework.

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