C# 学习笔记（16）ComboBox下拉列表框宽度自适应

Posted 2021-08-13 不咸不要钱

C# 学习笔记（16）ComboBox下拉列表框宽度自适应

当下拉列表框中内容宽度大于下拉列表框宽度时

下拉列表框不能将内容全部显示出来

可以在下拉时，对下拉列表框内容进行重绘

        /// <summary>
        /// 列表项下拉窗口宽度自适应
        /// </summary>
        /// <param name="comboBox"></param>
        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 comboBox1_DropDown(object sender, EventArgs e)
        {
            AdjustComboBoxDropDownListWidth(comboBox1);
        }