Getting this error, Can anyone help me?

I am trying to split an entire doc into useful material and non-useful material, however I am encountering this problem when i am trying to use the function, can someone tell me what the problem is?

Get_Data_From_Appointment_Letter.xaml: Compiler error(s) encountered processing expression “substringValue.Split(vbLf)(0)”.
Option Strict On disallows implicit conversions from ‘String’ to ‘Char’.

You can use:
substringValue.Split({vbLf}, StringSplitOptions.RemoveEmptyEntries)
substringValue.Split({vbLf}, StringSplitOptions.None)

the reason comes from following. vbLf is returning a string. The method signature requires it different. Have a look on the reference: