You undoubtedly have this line at the top of your code file:
Imports Microsoft.VisualBasic
Remove it, and your code stops compiling. Why? Because you're using VB6-like constructs that this namespace provides compatibility for.
More precisely, the MsgBox function. Use the MessageBox class in the Microsoft.Windows.Forms namespace instead, for a much more .NET-idiomatic invocation:
MessageBox.Show(String.Format("..."))
LBound and UBound will also stop compiling without the Microsoft.VisualBasic namespace imported.
Arrays in VB.NET are always 0-based, and an array's length can be determined using its... Length property: that's just one of the awesome implications of .NET's everything is an object.
Therefore, instead of this:
Dim lower As Integer = LBound(readResult) Dim upper As Integer = UBound(readResult) For i = lower To upper
You can do that:
For i = 0 To readResult.Length - 1
Also, instead of using ReDim to resize an array:
Dim multipliedResult As Integer() ReDim multipliedResult(0 To upper)
You could use the more idiomatic Array.Resize(ref multipliedResult, readResult.Length)... but then, why resize the array when you could just declare it with the appropriate length in the first place? Or better, why even use an array, when you could use a List(Of String) and just .Add values and let the framework deal with the underlying array? =)
Now, the array itself is obtained using the Split function, also a courtesy of Microsoft.VisualBasic - the .NET-idiomatic way to split a string is to use the Split method, available on any instance of any String object - because yes, even a String is an object in .NET!
Dim a As String = "foo bar baz"
Dim b As String() = a.Split(new String(){Environment.NewLine}, StringSplitOptions.None)
But you don't even need to Split anything, because you can ReadAllLines instead of ReadAllText, and work with a string array directly - add Imports System.IO at the top of the module, and reduce the wordiness of System.IO.File, too:
Dim readResult As String() = File.ReadAllLines(inputFile)
Another thing that makes your VB.NET feel like VBA/VB6 code, is how you're returning from a function:
If inputNumber Mod 2 = 0 Then inputNumber = inputNumber * 2 MultiplyEvenNumbers = inputNumber
In VB.NET, you use the Return keyword instead:
If inputNumber Mod 2 = 0 Then inputNumber = inputNumber * 2
Return inputNumber
But there's more: VB.NET has combined assignment operators, so instead of this:
inputNumber = inputNumber * 2
You can do this:
inputNumber *= 2
So to increment by one, you can't quite do i++ like you would in C#, but you can combine the + and = and do i += 1 to increment, and i -= 1 to decrement.
Lastly, idiomatic .net code will always have Option Explicit and Option Strict turned on.