Public Class MainForm

    Private Sub MainForm_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load

    End Sub

    Private Sub btnCheck_Click(sender As System.Object, e As System.EventArgs) Handles btnCheck.Click
        Dim state As Boolean = CheckifFileisEncoded(txtFilePath.Text)
        If state = True Then
            btnEncode.Enabled = False
            btnDecode.Enabled = True
            MsgBox("Encoded")
        Else
            btnDecode.Enabled = False
            btnEncode.Enabled = True
            MsgBox("Decoded")
        End If
        Dim fileReader As New IO.StreamReader(txtFilePath.Text)
        rtbContent.Text = fileReader.ReadToEnd()
        fileReader.Close()
    End Sub

    Private Sub btnEncode_Click(sender As System.Object, e As System.EventArgs) Handles btnEncode.Click
        If My.Computer.FileSystem.FileExists(txtFilePath.Text) Then
            Dim state As Boolean = EncodeTextFile(txtFilePath.Text)
            If state = True Then
                btnEncode.Enabled = False
                btnDecode.Enabled = True
                MsgBox("Encoded")
            Else
                btnDecode.Enabled = False
                btnEncode.Enabled = True
                MsgBox("Decoded")
            End If
            Dim fileReader As New IO.StreamReader(txtFilePath.Text)
            rtbContent.Text = fileReader.ReadToEnd()
            fileReader.Close()
        End If
    End Sub

    Private Sub btnDecode_Click(sender As System.Object, e As System.EventArgs) Handles btnDecode.Click
        If My.Computer.FileSystem.FileExists(txtFilePath.Text) Then
            Dim state As Boolean = DecodeTextFile(txtFilePath.Text)
            If state = True Then
                btnDecode.Enabled = False
                btnEncode.Enabled = True
                MsgBox("Decoded")  
            Else
                btnEncode.Enabled = False
                btnDecode.Enabled = True
                MsgBox("Encoded")
            End If
            Dim fileReader As New IO.StreamReader(txtFilePath.Text)
            rtbContent.Text = fileReader.ReadToEnd()
            fileReader.Close()
        End If
    End Sub

    Public ReadOnly Property CheckifFileisEncoded(ByVal filePath As String) As Boolean
        Get
            Dim newTextReader As String = My.Computer.FileSystem.ReadAllText(filePath)
            Dim str As [String] = newTextReader
            Try
                Dim data As Byte() = Convert.FromBase64String(str)
                Return (str.Replace(" ", "").Length Mod 4 = 0)
            Catch ex As Exception
                Return False
            End Try
        End Get
    End Property

    Public ReadOnly Property EncodeTextFile(ByVal filePath As String) As Boolean
        Get
            Try
                Dim newTextReader As String = My.Computer.FileSystem.ReadAllText(filePath)
                Dim enc As New System.Text.UnicodeEncoding
                Dim buffer As Byte() = enc.GetBytes(newTextReader)
                Dim newTextWriter As String = Convert.ToBase64String(buffer)
                Dim newStreamWriter As New System.IO.StreamWriter(filePath, False)
                newStreamWriter.Write(newTextWriter)
                newStreamWriter.Close()
                Return True
            Catch ex As Exception
                Return False
            End Try
        End Get
    End Property

    Public ReadOnly Property DecodeTextFile(ByVal filePath As String) As Boolean
        Get
            Try
                Dim newTextReader As String = My.Computer.FileSystem.ReadAllText(filePath)
                Dim enc As New System.Text.UnicodeEncoding
                Dim buffer As Byte() = Convert.FromBase64String(newTextReader)
                Dim newTextWriter As String = enc.GetString(buffer)
                Dim newStreamWriter As New System.IO.StreamWriter(filePath, False)
                newStreamWriter.Write(newTextWriter)
                newStreamWriter.Close()
                Return True
            Catch ex As Exception
                Return False
            End Try
        End Get
    End Property

End Class