如何设置ComboBox的高度？

Question

我在表单上有一个ComboBox,其默认高度为21.如何更改它？

Answer 1

ComboBox自动调整大小以适应字体.关闭它不是一种选择.如果你想要它更大,那么给它一个更大的字体.

Answer 2

设置DrawMode为OwnerDrawVariable.但是,ComboBox的自定义会导致其他问题.有关如何完成此操作的教程,请参阅此链接:

http://www.csharphelp.com/2006/09/listbox-control-in-c/

OwnerDrawVariable示例代码:https: //msdn.microsoft.com/en-us/library/system.windows.forms.combobox.drawitem%28v=vs.110%29.aspx

完成后,您需要设置ItemHeight组合框的属性以设置组合框的有效高度.

Answer 3

正如另一种选择,如果你想在ComboBox不增加字体大小的情况下增加高度或者不必担心自己绘制所有内容,可以使用简单的Win32 API调用来增加高度,如下所示:

using System;
using System.Runtime.InteropServices;
using System.Windows.Forms;

namespace Win32ComboBoxHeightExample
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        [DllImport("user32.dll")]
        static extern IntPtr SendMessage(IntPtr hWnd, UInt32 Msg, Int32 wParam, Int32 lParam);
        private const Int32 CB_SETITEMHEIGHT = 0x153;

        private void SetComboBoxHeight(IntPtr comboBoxHandle, Int32 comboBoxDesiredHeight)
        {
            SendMessage(comboBoxHandle, CB_SETITEMHEIGHT, -1, comboBoxDesiredHeight);
        }

        private void button1_Click(object sender, EventArgs e)
        {
            SetComboBoxHeight(comboBox1.Handle, 150);
            comboBox1.Refresh();
        }
    }
}

结果:

Answer 4

为此，您需要将 或 设置DrawMode为OwnerDrawVariable或OwnerDrawFixed并手动绘制项目。这可以通过一个非常简单的类来完成。

此示例将允许您使用ItemHeightComboBox 的属性，无论字体大小如何。我添加了一个奖励属性TextAlign，它也可以让您将项目居中。

值得一提的是，您必须将所选项目设置DropDownStyle为DropDownList尊重我们的自定义设置。

// The standard combo box height is determined by the font. This means, if you want a large text box, you must use a large font.
// In our class, ItemHeight will now determine the height of the combobox with no respect to the combobox font.
// TextAlign can be used to align the text in the ComboBox
class UKComboBox : ComboBox
{

    private StringAlignment _textAlign = StringAlignment.Center;
    [Description("String Alignment")]
    [Category("CustomFonts")]
    [DefaultValue(typeof(StringAlignment))]
    public StringAlignment TextAlign
    {
        get { return _textAlign; }
        set
        {
            _textAlign = value;
        }
    }

    private int _textYOffset = 0;
    [Description("When using a non-centered TextAlign, you may want to use TextYOffset to manually center the Item text.")]
    [Category("CustomFonts")]
    [DefaultValue(typeof(int))]
    public int TextYOffset
    {
        get { return _textYOffset; }
        set
        {
            _textYOffset = value;
        }
    }


    public UKComboBox()
    {
            // Set OwnerDrawVariable to indicate we will manually draw all elements.
            this.DrawMode = System.Windows.Forms.DrawMode.OwnerDrawVariable;
            // DropDownList style required for selected item to respect our DrawItem customizations.
            this.DropDownStyle = ComboBoxStyle.DropDownList;
            // Hook into our DrawItem & MeasureItem events
            this.DrawItem +=
                new DrawItemEventHandler(ComboBox_DrawItem);
            this.MeasureItem +=
                new MeasureItemEventHandler(ComboBox_MeasureItem);

    }

    // Allow Combo Box to center aligned and manually draw our items
    private void ComboBox_DrawItem(object sender, DrawItemEventArgs e)
    {


        // Draw the background
        e.DrawBackground();

        // Draw the items
        if (e.Index >= 0)
        {
            // Set the string format to our desired format (Center, Near, Far)
            StringFormat sf = new StringFormat();
            sf.LineAlignment = _textAlign;
            sf.Alignment = _textAlign;

            // Set the brush the same as our ForeColour
            Brush brush = new SolidBrush(this.ForeColor);

            // If this item is selected, draw the highlight
            if ((e.State & DrawItemState.Selected) == DrawItemState.Selected)
                brush = SystemBrushes.HighlightText;

            // Draw our string including our offset.
            e.Graphics.DrawString(this.Items[e.Index].ToString(), this.Font, brush, 
                new RectangleF(e.Bounds.X, e.Bounds.Y + _textYOffset, e.Bounds.Width, e.Bounds.Height), sf);
        }

    }


    // If you set the Draw property to DrawMode.OwnerDrawVariable, 
    // you must handle the MeasureItem event. This event handler 
    // will set the height and width of each item before it is drawn. 
    private void ComboBox_MeasureItem(object sender,System.Windows.Forms.MeasureItemEventArgs e)
    {
        // Custom heights per item index can be done here.
    }

}

现在我们可以分别完全控制组合框的字体和高度。我们不再需要使用大字体来调整组合框的大小。