How To Add A Syntax Highlighter In VB.NET

how to add a syntax highlighter in vb.net this is the easiest and the best way to do it so lets get start

open your visual basic 2008/2010 now make a new project or if you have a project to add this syntax highlighter just open your project anyway i will go with a new project create a new project and name it whatever you want and go to the form and make a new class and paste this code inside the class

Public Class SyntaxRTB

    Inherits System.Windows.Forms.RichTextBox

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

    Private Declare Function LockWindowUpdate Lib "user32" (ByVal hWnd As Integer) As Integer

    Private _SyntaxHighlight_CaseSensitive As Boolean = False

    Private Words As New DataTable

    'Contains Windows Messages for the SendMessage API call
    Private Enum EditMessages
        LineIndex = 187
        LineFromChar = 201
        GetFirstVisibleLine = 206
        CharFromPos = 215
        PosFromChar = 1062
    End Enum

    Protected Overrides Sub OnTextChanged(ByVal e As System.EventArgs)
        ColorVisibleLines()
    End Sub

    Public Sub ColorRtb()
        Dim FirstVisibleChar As Integer
        Dim i As Integer = 0

        While i < Me.Lines.Length
            FirstVisibleChar = GetCharFromLineIndex(i)
            ColorLineNumber(i, FirstVisibleChar)
            i += 1
        End While
    End Sub

    Public Sub ColorVisibleLines()
        Dim FirstLine As Integer = FirstVisibleLine()
        Dim LastLine As Integer = LastVisibleLine()
        Dim FirstVisibleChar As Integer

        If (FirstLine = 0) And (LastLine = 0) Then
            'If there is no text it will error, so exit the sub
            Exit Sub
        Else
            While FirstLine < LastLine
                FirstVisibleChar = GetCharFromLineIndex(FirstLine)
                ColorLineNumber(FirstLine, FirstVisibleChar)
                FirstLine += 1
            End While
        End If

    End Sub

    Public Sub ColorLineNumber(ByVal LineIndex As Integer, ByVal lStart As Integer)
        Dim i As Integer = 0
        Dim Instance As Integer
        Dim LeadingChar, TrailingChar As String
        Dim SelectionAt As Integer = Me.SelectionStart
        Dim MyRow As DataRow
        Dim Line() As String, MyI As Integer, MyStr As String

        ' Lock the update
        LockWindowUpdate(Me.Handle.ToInt32)

        MyI = lStart

        If CaseSensitive Then
            Line = Split(Me.Lines(LineIndex).ToString, " ")
        Else
            Line = Split(Me.Lines(LineIndex).ToLower, " ")
        End If

        For Each MyStr In Line
            Me.SelectionStart = MyI
            Me.SelectionLength = MyStr.Length

            If Words.Rows.Contains(MyStr) Then
                MyRow = Words.Rows.Find(MyStr)
                If (Not CaseSensitive) Or (CaseSensitive And MyRow("Word") = MyStr) Then
                    Me.SelectionColor = Color.FromName(MyRow("Color"))
                End If
            Else
                Me.SelectionColor = Color.Black
            End If

            MyI += MyStr.Length + 1
        Next

        ' Restore the selectionstart
        Me.SelectionStart = SelectionAt
        Me.SelectionLength = 0
        Me.SelectionColor = Color.Black

        ' Unlock the update
        LockWindowUpdate(0)
    End Sub

    Public Function GetCharFromLineIndex(ByVal LineIndex As Integer) As Integer
        Return SendMessage(Me.Handle, EditMessages.LineIndex, LineIndex, 0)
    End Function

    Public Function FirstVisibleLine() As Integer
        Return SendMessage(Me.Handle, EditMessages.GetFirstVisibleLine, 0, 0)
    End Function

    Public Function LastVisibleLine() As Integer
        Dim LastLine As Integer = FirstVisibleLine() + (Me.Height / Me.Font.Height)

        If LastLine > Me.Lines.Length Or LastLine = 0 Then
            LastLine = Me.Lines.Length
        End If

        Return LastLine
    End Function

    Public Sub New()
        Dim MyRow As DataRow
        Dim arrKeyWords() As String, strKW As String

        Me.AcceptsTab = True

        ''Load all the keywords and the colors to make them 
        Words.Columns.Add("Word")
        Words.PrimaryKey = New DataColumn() {Words.Columns(0)}
        Words.Columns.Add("Color")

        arrKeyWords = New String() {"select", "insert", "delete", _
           "truncate", "from", "where", "into", "inner", "update", _
           "outer", "on", "is", "declare", "set", "use", "values", "as", _
           "order", "by", "drop", "view", "go", "trigger", "cube", _
           "binary", "varbinary", "image", "char", "varchar", "text", _
           "datetime", "smalldatetime", "decimal", "numeric", "float", _
           "real", "bigint", "int", "smallint", "tinyint", "money", _
           "smallmoney", "bit", "cursor", "timestamp", "uniqueidentifier", _
           "sql_variant", "table", "nchar", "nvarchar", "ntext", "left", _
           "right", "like", "and", "all", "in", "null", "join", "not", "or"}

        For Each strKW In arrKeyWords
            MyRow = Words.NewRow()
            MyRow("Word") = strKW
            MyRow("Color") = Color.LightCoral.Name
            Words.Rows.Add(MyRow)
        Next

    End Sub

    Public Property CaseSensitive() As Boolean
        Get
            Return _SyntaxHighlight_CaseSensitive
        End Get
        Set(ByVal Value As Boolean)
            _SyntaxHighlight_CaseSensitive = Value
        End Set
    End Property

End Class

now debug and stop debugging and see the toolbox you will see something like this

add the tool "syntaxRTB" in to your form and you can replace it with richtextbox or textbox just rename it now debug and paste some codes inside the tool and it will work for sure .

preview - 

hope this helped you