How to change Celsius to Fahrenheit

I am not quite understanding I am working with Microsoft Visual basic .Net programming and I Have this so far

 Sub Main()
        Dim fahrenheit, celsius As Double
        Console.WriteLine("Enter a value for fahrenheit tempature:")
        fahrenheit = Convert.ToDouble(Console.ReadLine())
        celsius = 5 / 9 * (fahrenheit - 32)
        celsius = Math.Round(celsius, 1)
        Console.WriteLine(fahrenheit & " F = " & celsius & " C")

Now I have to add similar lines of code to change Celsius temp to Fahrenheit now do I just repeat what I have or is there another way I am exploring to understand this.I have tried a few things but it is not working.. Can someone explain what I am doing wrong.. and I suppose to use the else if?

Sub Main()
    Dim fahrenheit, celsius As Double
    Console.WriteLine("Enter a value for fahrenheit tempature:")
    fahrenheit = Convert.ToDouble(Console.ReadLine())
    celsius = 5 / 9 * (fahrenheit - 32)
    fahrenheit = celsius * 9 / 5 + 32
    celsius = Math.Round(celsius, 1)
    Console.WriteLine(fahrenheit &开发者_C百科amp; " F = " & celsius & " C")
End Sub

Ok this is what I have no when the black box comes run when you debug it it only states fahrenheit how can I also get it to read celsius too or do I have to just start clear and make each one as there own.

If this is a learning exercise, why not produce a function for each?

Function GetCelsiusForFahrenheit(ByVal fahrenheit as Double) As Double
    Return (5/9) * (fahrenheit - 32)
End Function

Function GetFahrenheitForCelsius(ByVal celsius as Double) As Double
    Return  (9/5) * celsius  + 32
End Function

why do you not use the "other direction formula" for this? So that would be

fahrenheit = (9 / 5 * celsius) + 32