writing let in vb 2013

I am trying to write Let in vb and it won't let me do it, it keeps erasing itself. Do i need to download a package or something?

For example:

If Not currentDirectory = "" Then Dim lines() As String = System.IO.File.ReadAllLines(currentDirectory)

            Dim data = From line In lines


          Let  nam = line.Split(","c)(0)
          Let  num = line.Split(","c)(1)
        Order By nam Ascending 

        Select nam, num

        DataGridView1.DataSource = data.ToList

        DataGridView1.CurrentCell = Nothing

        DataGridView1.Columns("nam").HeaderText = "Name"

        DataGridView1.Columns("num").HeaderText = "Phone Number"


    End If

it will not let me type "Let"