VB.net中richtextbox控件中如何改变选中行的背景色
如题，是改变行的背景色，不是行中的字符（中/英文）颜色改变哈。
找了些方法，只能改变行中字符的颜色，暂时没找到改变一行背景的颜色，在这里求助大家了。
[解决办法]

Imports System.Runtime.InteropServices

Public Class Form1

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim cf As New CHARFORMAT2A
        Dim colr As Color = Color.Red
        Dim ret As Integer
        With cf
            .cbSize = Marshal.SizeOf(cf) 'setup the size of the character format

            .dwMask = CFM_BACKCOLOR 'what to test

            .crBackColor = Drawing.ColorTranslator.ToWin32(colr)
            ret = SendMessage(Me.RichTextBox1.Handle, EM_SETCHARFORMAT, SCF_SELECTION, cf)
        End With 'CF
    End Sub

    Private Const WM_USER As Integer = &H400

    Private Const CFM_BACKCOLOR As Integer = &H4000000

    Private Const EM_GETCHARFORMAT As Integer = (WM_USER + 58)

    Private Const EM_SETCHARFORMAT As Integer = (WM_USER + 68)

    Private Const SCF_SELECTION As Integer = &H1&

    Private Const LF_FACESIZE As Integer = 32

    Private Declare Function SendMessage Lib "user32" Alias "SendMessageA" (ByVal hwnd As Integer, _
                                                                            ByVal wMsg As Integer, _
                                                                            ByVal wParam As Integer, _
                                                                            ByVal lParam As CHARFORMAT2A) As Integer

    <StructLayout(LayoutKind.Sequential, Pack:=4)> _
Public Class CHARFORMAT2A
        Public cbSize As Integer = Marshal.SizeOf(GetType(CHARFORMAT2A))
        Public dwMask As Integer
        Public dwEffects As Integer
        Public yHeight As Integer
        Public yOffset As Integer
        Public crTextColor As Integer
        Public bCharSet As Byte
        Public bPitchAndFamily As Byte
        <MarshalAs(UnmanagedType.ByValArray, SizeConst:=&H20)> _
        Public szFaceName As Byte() = New Byte(&H20 - 1) {}
        Public wWeight As Short
        Public sSpacing As Short
        Public crBackColor As Integer
        Public lcid As Integer 
 
        Public dwReserved As Integer
        Public sStyle As Short
        Public wKerning As Short
        Public bUnderlineType As Byte
        Public bAnimation As Byte
        Public bRevAuthor As Byte
    End Class



End Class