c#.net 文本编辑控件——设置RichTextBox的字体和字体大小

上一篇文章讨论了有关设置字体格式：粗体、斜体和下划线的问题，本文将要继续讨论的是如何设置字体和字体大小。字体和字体大小的设置与字体格式的设置道理是相同的，也要区分被选中文本的SelectionFont是否为空的问题。下面分别是设置字体种类和字体大小的相关代码。

        /// <summary>
        /// 设置字体种类,对应于字体下拉框选项
         /// </summary>
        /// <param name="fontName">被选中的字体名</param>
        private void ChangeFont(string fontName)
        {
            if (fontName == string.Empty)
                throw new System.Exception("字体名称参数错误，不能为空");
            RichTextBox tempRichTextBox = new RichTextBox();  //用于保存被选中文本的副本
              
              //curRichTextBox是当前文本，即原型
              int curRtbStart = curRichTextBox.SelectionStart;  
              int len = curRichTextBox.SelectionLength;
            int tempRtbStart = 0;
            Font font = curRichTextBox.SelectionFont;
            if (len <= 1 && null != font)
            {
                curRichTextBox.SelectionFont = new Font(fontName, font.Size, font.Style);
                return;
            }
            tempRichTextBox.Rtf = curRichTextBox.SelectedRtf;
            for (int i = 0; i < len; i++)  //逐个设置字体种类
              {
                tempRichTextBox.Select(tempRtbStart + i, 1);
                tempRichTextBox.SelectionFont = 
                    new Font(fontName, tempRichTextBox.SelectionFont.Size,     
                             tempRichTextBox.SelectionFont.Style);
            }
            //将副本内容插入到到原型中
            tempRichTextBox.Select(tempRtbStart, len);
            curRichTextBox.SelectedRtf = tempRichTextBox.SelectedRtf;  
              curRichTextBox.Select(curRtbStart, len);
            curRichTextBox.Focus();
        }

        /// <summary>
        /// 设置字体大小,对应于字号下拉框选项
         /// </summary>
        /// <param name="fontSize">被选中的字号</param>
        private void ChangeFontSize(float fontSize)
        {
            if (fontSize <= 0.0)
                throw new InvalidProgramException("字号参数错误，不能小于等于0.0");
            RichTextBox tempRichTextBox = new RichTextBox();
            int curRtbStart = curRichTextBox.SelectionStart;
            int len = curRichTextBox.SelectionLength;
            int tempRtbStart = 0;
            Font font = curRichTextBox.SelectionFont;
            if (len <= 1 && null != font)
            {
                curRichTextBox.SelectionFont = new Font(font.Name, fontSize, font.Style);
                return;
            }
            tempRichTextBox.Rtf = curRichTextBox.SelectedRtf;
            for (int i = 0; i < len; i++)
            {
                tempRichTextBox.Select(tempRtbStart + i, 1);
                tempRichTextBox.SelectionFont = 
                    new Font(tempRichTextBox.SelectionFont.Name, 
                             fontSize, tempRichTextBox.SelectionFont.Style);
            }
            tempRichTextBox.Select(tempRtbStart, len);
            curRichTextBox.SelectedRtf = tempRichTextBox.SelectedRtf;
            curRichTextBox.Select(curRtbStart, len);
            curRichTextBox.Focus();
        }