[StructLayout(LayoutKind.Sequential), ComVisible(true)]

public struct HandleRef

{

    internal object m_wrapper;

    internal IntPtr m_handle;

    public HandleRef(object wrapper, IntPtr handle)

    {

        this.m_wrapper = wrapper;

        this.m_handle = handle;

    }



    public object Wrapper

    {

        get

        {

            return this.m_wrapper;

        }

    }

    public IntPtr Handle

    {

        get

        {

            return this.m_handle;

        }

    }

    public static explicit operator IntPtr(HandleRef value)

    {

        return value.m_handle;

    }



    public static IntPtr ToIntPtr(HandleRef value)

    {

        return value.m_handle;

    }

}



[StructLayout(LayoutKind.Sequential, Pack=4)]

public class CHARFORMATA

{

    public int cbSize = Marshal.SizeOf(typeof(CHARFORMATA));

    public int dwMask;

    public int dwEffects;

    public int yHeight;

    public int yOffset;

    public int crTextColor;

    public byte bCharSet;

    public byte bPitchAndFamily;

    [MarshalAs(UnmanagedType.ByValArray, SizeConst=0x20)]

    public byte[] szFaceName = new byte[0x20];

}



[DllImport("user32.dll", CharSet=CharSet.Auto)]

public static extern IntPtr SendMessage(HandleRef hWnd, int msg, int wParam, [In, Out, MarshalAs(UnmanagedType.LPStruct)] CHARFORMATA lParam); 

private void InitializeComponent()

        {

            this.richTextBox1 = new System.Windows.Forms.RichTextBox();

            this.richTextBox2 = new System.Windows.Forms.RichTextBox();

            this.SuspendLayout();

            // 

            // richTextBox1

            this.richTextBox1.Font = new Font("隶书", 13, System.Drawing.FontStyle.Regular)

}

        int start = 0;

        int end = 0;

        public testForm()

        {

            InitializeComponent();

            richTextBox1.TextChanged +=new EventHandler(richTextBox1_TextChanged);

            richTextBox1.SelectionChanged += new EventHandler(richTextBox1_SelectionChanged);

        }



        void richTextBox1_SelectionChanged(object sender, EventArgs e)

        {

            start = end;

            end = richTextBox1.SelectionStart;

        }



        void richTextBox1_TextChanged(object sender, EventArgs e)

        {

            if (end > start)

            {

                richTextBox1.Select(start, end - start);

            }

            richTextBox1.SelectionFont = new Font("宋体", 12);

            richTextBox1.Select(start, 0);

        }