功能：弹出字体设置对话框
主要属性：
Font：选择的字体。

public  void  copy():文本框中的当前选定内容复制到“剪贴板”
public  void  Paste()：用剪贴板的内容替换文本框中的当前选定内容。
public  void  Cut()：将文本框中的当前选定内容移动到“剪贴板”中。

“字体”菜单事件代码如下：
private void 字体ToolStripMenuItem_Click(object sender, EventArgs e)
        {
            fontDialog1.ShowDialog();//显示字体对话框
            if (fontDialog1.Font != null)
            { textContent.Font=fontDialog1.Font; }
        }

“复制”、“剪切”、“粘贴”菜单代码编写如下：
private void 复制ToolStripMenuItem_Click(object sender, EventArgs e)
        {
            if (textContent.SelectedText != null)
            {
                textContent.Copy();
            }
        }
        private void 剪切ToolStripMenuItem_Click(object sender, EventArgs e)
        {
            if (textContent.SelectedText != null)
            {
                textContent.Cut();
            }
        }
        private void 粘贴ToolStripMenuItem_Click(object sender, EventArgs e)
        {
            textContent.Paste();
        }

private void 新建ToolStripMenuItem_Click(object sender, EventArgs e)
        {
            if (openFileDialog1.FileName != null && textContent.Modified == true && MessageBox.Show("文本内容已更改\n是否保存修改？", "信息提示", MessageBoxButtons.OKCancel) == DialogResult.OK)
            {
                saveFileDialog1.ShowDialog();
                if (saveFileDialog1.FileName != null)
                {
                    try
                    {
                    string filename = saveFileDialog1.FileName;
                    StreamWriter sw = new StreamWriter(filename);
                    sw.Write(this.textContent.Text);
                    sw.Close();
                     }catch(Exception) { }
                }
            }
            textContent.Clear();
        }
    private void 退出ToolStripMenuItem_Click(object sender, EventArgs e)
        {
            if (openFileDialog1.FileName != null && textContent.Modified == true && MessageBox.Show("文本内容已更改\n是否保存修改？", "信息提示", MessageBoxButtons.OKCancel) == DialogResult.OK)
            {
                saveFileDialog1.ShowDialog();
                if (saveFileDialog1.FileName != null)
                {
                    try
                    {
                        string filename = saveFileDialog1.FileName;
                        StreamWriter sw = new StreamWriter(filename);
                        sw.Write(this.textContent.Text);
                        sw.Close();
                    }
                    catch (Exception) { }
                }
            }
            this.Close();
        }