StreamString(pipeClient) throws error Type is not defined

I am trying to unlock the machine by passing user id and password in UiPath when scheduled bot trying to run the process in locked system

Below is my code

    'Create a new pipe client
    Using pipeClient As New System.IO.Pipes.NamedPipeClientStream(
        ".",
        "CredentialProviderPipe",
        PipeDirection.InOut,
        PipeOptions.None,
        System.Security.Principal.TokenImpersonationLevel.Impersonation)

        'Attempt to connect to it
        pipeClient.Connect(10000)
        'Send credentials
        Dim dom As String
         If Domain = "" Then
            dom = Environment.UserDomainName
        Else
            dom = Domain
        End If

        Dim ss As New StreamString(pipeClient)

        ss.WriteString(String.Format("LOGON{0}{1}{0}{2}{0}{3}", vbLf, dom, Username, Password))

        'Wait for reply
        Using pr As New StreamReader(pipeClient, System.Text.Encoding.Unicode)
            Response = pr.ReadLine()
            If Response = "OK" OrElse Response = "UNKNOWN" Then Return

            ErrorCode = pr.ReadLine()
            ErrorMessage = pr.ReadLine()
        End Using
    End Using
Catch ex As TimeoutException
    Response = "ERROR"
    ErrorCode = "0x80131505"
    ErrorMessage = ex.Message
Catch ex As Exception
    Response = "ERROR"
    ErrorCode = ""
    ErrorMessage = ex.Message
End Try

I am getting below error that error BC30002: Type StringStream is not defined.

I dont know how to resolve the issue. Please help

It looks like all those uses of StreamString are based on the example here, which includes the definition of that class as below:

' Defines the data protocol for reading and writing strings on our stream
Public Class StreamString
    Private ioStream As Stream
    Private streamEncoding As UnicodeEncoding

    Public Sub New(ioStream As Stream)
        Me.ioStream = ioStream
        streamEncoding = New UnicodeEncoding(False, False)
    End Sub

    Public Function ReadString() As String
        Dim len As Integer = 0
        len = CType(ioStream.ReadByte(), Integer) * 256
        len += CType(ioStream.ReadByte(), Integer)
        Dim inBuffer As Array = Array.CreateInstance(GetType(Byte), len)
        ioStream.Read(inBuffer, 0, len)

        Return streamEncoding.GetString(inBuffer)
    End Function

    Public Function WriteString(outString As String) As Integer
        Dim outBuffer() As Byte = streamEncoding.GetBytes(outString)
        Dim len As Integer = outBuffer.Length
        If len > UInt16.MaxValue Then
            len = CType(UInt16.MaxValue, Integer)
        End If
        ioStream.WriteByte(CType(len \ 256, Byte))
        ioStream.WriteByte(CType(len And 255, Byte))
        ioStream.Write(outBuffer, 0, outBuffer.Length)
        ioStream.Flush()

        Return outBuffer.Length + 2
    End Function
End Class