private void AdjustComboBoxDropDownListWidth(object comboBox)
...{
Graphics g = null; Font font = null; try
...{ ComboBox senderComboBox = null; if (comboBox is ComboBox) senderComboBox = (ComboBox)comboBox; else if (comboBox is ToolStripComboBox) senderComboBox = ((ToolStripComboBox)comboBox).ComboBox; else return; int width = senderComboBox.Width; g = senderComboBox.CreateGraphics(); font = senderComboBox.Font; //checks if a scrollbar will be displayed. //If yes, then get its width to adjust the size of the drop down list. int vertScrollBarWidth = (senderComboBox.Items.Count > senderComboBox.MaxDropDownItems) ? SystemInformation.VerticalScrollBarWidth : 0; int newWidth; foreach (object s in senderComboBox.Items) //Loop through list items and check size of each items. ...{ if (s != null) ...{ newWidth = (int)g.MeasureString(s.ToString().Trim(), font).Width + vertScrollBarWidth; if (width < newWidth) width = newWidth; //set the width of the drop down list to the width of the largest item.
} } senderComboBox.DropDownWidth = width; } catch ...{ } finally ...{ if (g != null) g.Dispose(); }
}private void button1_Click(object sender, EventArgs e) ...{ comboBox1.Items.Add("美国"); comboBox1.Items.Add("中华人民共和国"); comboBox1.Items.Add("新疆维吾尔族自治区"); AdjustComboBoxDropDownListWidth(comboBox1); }using System;using System.Collections.Generic;using System.ComponentModel;using System.Drawing;using System.Data;using System.Text;using System.Windows.Forms;namespace WindowsApplication2...{ class MyComboBox : ComboBox ...{ protected override void OnDropDown(EventArgs e) ...{ base.OnDropDown(e); AdjustComboBoxDropDownListWidth(); //调整comboBox的下拉列表的大小 } private void AdjustComboBoxDropDownListWidth() ...{ Graphics g = null; Font font = null; try ...{ int width = this.Width; g = this.CreateGraphics(); font = this.Font; //checks if a scrollbar will be displayed. //If yes, then get its width to adjust the size of the drop down list. int vertScrollBarWidth = (this.Items.Count > this.MaxDropDownItems) ? SystemInformation.VerticalScrollBarWidth : 0; int newWidth; foreach (object s in this.Items) //Loop through list items and check size of each items. ...{ if (s != null) ...{ newWidth = (int)g.MeasureString(s.ToString().Trim(), font).Width + vertScrollBarWidth; if (width < newWidth) width = newWidth; //set the width of the drop down list to the width of the largest item. } } this.DropDownWidth = width; } catch ...{ } finally ...{ if (g != null) g.Dispose(); } } }}