更改 ComboBox 突出显示的颜色 [英] Changing the Color of ComboBox highlighting

问题描述

我正在尝试在 C# Windows Forms 应用程序的 ComboBox 下拉列表中更改突出显示的颜色.我在整个网络上搜索了答案，到目前为止我发现的最佳选择是在绘制所选项目时绘制所需颜色的矩形.

I am trying to work around changing the color of highlighting in a ComboBox dropdown on a C# Windows Forms application. I have searched the whole web for an answer, and the best option i found so far was to draw a rectangle of the desired color when the item that is selected is being drawn.

Class Search
{
    Public Search()
    {
    }

    private void addFilter()
    {
        ComboBox field = new ComboBox();

        field.Items.AddRange(new string[] { "Item1", "item2" });
        field.Text = "Item1";
        field.DropDownStyle = ComboBoxStyle.DropDownList;
        field.FlatStyle = FlatStyle.Flat;
        field.BackColor = Color.FromArgb(235, 235, 235);
        field.DrawMode = DrawMode.OwnerDrawFixed;
        field.DrawItem += field_DrawItem;
    }

    private void field_DrawItem(object sender, DrawItemEventArgs e)
    {
        if (e.Index >= 0)
        {
            ComboBox combo = sender as ComboBox;

            if (e.Index == combo.SelectedIndex)
                e.Graphics.FillRectangle(new SolidBrush(Color.Gray),
                                         e.Bounds
                                        );
            else
                e.Graphics.FillRectangle(new SolidBrush(combo.BackColor),
                                         e.Bounds
                                        );

            e.Graphics.DrawString(combo.Items[e.Index].ToString(), e.Font,
                                  new SolidBrush(combo.ForeColor),
                                  new Point(e.Bounds.X, e.Bounds.Y)
                                 );
        }
    }
}

这段代码的问题是，一旦选择了下拉列表中的另一个项目，我绘制矩形的另一个项目仍然是我想要突出显示的颜色.然后我尝试保存最后绘制的 Item 并重新绘制它:

The problem with this code, is that once another Item in the dropdown is selected, the other Item I draw a rectangle is still with the color i want to highlight. Then i tried to save the last Item drawn and redraw it:

Class Search
{
    private DrawItemEventArgs lastDrawn;

    Public Search()
    {
        lastDrawn = null;
    }

    private void addFilter()
    {
        ComboBox field = new ComboBox();

        field.Items.AddRange(new string[] { "Item1", "item2" });
        field.Text = "Item1";
        field.DropDownStyle = ComboBoxStyle.DropDownList;
        field.FlatStyle = FlatStyle.Flat;
        field.BackColor = Color.FromArgb(235, 235, 235);
        field.DrawMode = DrawMode.OwnerDrawFixed;
        field.DrawItem += field_DrawItem;
    }

    private void field_DrawItem(object sender, DrawItemEventArgs e)
    {
        if (e.Index >= 0)
        {
            ComboBox combo = sender as ComboBox;
            if (e.Index == combo.SelectedIndex)
            {
                e.Graphics.FillRectangle(new SolidBrush(Color.Gray), e.Bounds);
                if(lastDrawn != null)
                    lastDrawn.Graphics.FillRectangle(new SolidBrush(combo.BackColor),
                                                 lastDrawn.Bounds
                                                );
                lastDrawn = e;
            }
            else
                e.Graphics.FillRectangle(new SolidBrush(combo.BackColor),
                                         e.Bounds
                                        );

            e.Graphics.DrawString(combo.Items[e.Index].ToString(), e.Font,
                                  new SolidBrush(combo.ForeColor),
                                  new Point(e.Bounds.X, e.Bounds.Y)
                                 );
        }
    }
}

由于lastDrawn.Bounds(类型不兼容)，该行返回错误

This line returns an error because of lastDrawn.Bounds (incompatible type)

lastDrawn.Graphics.FillRectangle(new SolidBrush(combo.BackColor),
                                                 lastDrawn.Bounds
                                                );

我觉得更改下拉菜单的高亮颜色是不可能的.提前致谢！

I am feeling that changing the highlight color of the dropdown is impossible. Thanks in advance!

推荐答案

如果您在项目中的多个地方使用 ComboBox，重复相同的代码是没有意义的DrawItem 事件一遍又一遍.只需将此类添加到您的项目中，您就会拥有一个新的 ComboBox 控件，该控件具有 HightlightColor 属性，这将使在整个项目中使用该控件变得更加容易:

In case you are using the ComboBox in more than one place in your project, it will not make sense to repeat the same code for DrawItem event over and over again. Just add this class to your project and you will have a new ComboBox control that has the HightlightColor property which will makes it easier to use the control all over the project:

class AdvancedComboBox : ComboBox
{
    new public System.Windows.Forms.DrawMode DrawMode { get; set; }
    public Color HighlightColor { get; set; }

    public AdvancedComboBox()
    {
        base.DrawMode = System.Windows.Forms.DrawMode.OwnerDrawFixed;
        this.HighlightColor = Color.Gray;
        this.DrawItem += new DrawItemEventHandler(AdvancedComboBox_DrawItem);
    }

    void AdvancedComboBox_DrawItem(object sender, DrawItemEventArgs e)
    {
        if (e.Index < 0)
            return;

        ComboBox combo = sender as ComboBox;
        if ((e.State & DrawItemState.Selected) == DrawItemState.Selected)
            e.Graphics.FillRectangle(new SolidBrush(HighlightColor),
                                     e.Bounds);
        else
            e.Graphics.FillRectangle(new SolidBrush(combo.BackColor),
                                     e.Bounds);

        e.Graphics.DrawString(combo.Items[e.Index].ToString(), e.Font,
                              new SolidBrush(combo.ForeColor),
                              new Point(e.Bounds.X, e.Bounds.Y));

        e.DrawFocusRectangle();
    }
}

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