Variable has been used before it has been assigned a value

Question

I can\'t find the answer to my specific problem anywhere so I figured I\'d open a new question.

I have a program that converts text between ASCII and Binary. It does thi

Answer 1

There's an easier way to do it:

Function BinaryStringToAscii(s As String) As String
    If s.Length Mod 8 <> 0 Then
        Throw New ArgumentException("String length is not a multiple of 8.")
    End If

    Dim sb As New Text.StringBuilder

    For i = 0 To s.Length - 1 Step 8
        Dim bin = s.Substring(i, 8)
        sb.Append(Chr(Convert.ToInt32(bin, 2)))
    Next

    Return sb.ToString()

End Function

It uses a StringBuilder as in the end you need a string, and there is no need to use an array or list. The Convert.ToInt32 function has a useful overload where you can specify the base (2, 8, 10 or 16) to convert a string from.

And the converse:

Function AsciiToBinaryString(s As String) As String
    Dim sb As New Text.StringBuilder
    For Each c In s
        sb.Append(Convert.ToString(Asc(c), 2).PadLeft(8, "0"c))
    Next

    Return sb.ToString()

End Function

Answer 2

You've declared an array, result, but the variable hasn't been assigned an instance of an array, so it's null. You can't add objects to a null array. Perhaps you meant this:

Dim result(BinarySubstrings.Length) As String

If you aren't sure about the size of result, consider using a List(Of String) as mentioned in the comments.

Answer 3

Using a List(Of String) is better because you don't need to know the size of the array.
Of course you need to initialize the List(Of String) before usage.

Function ConvertBinaryToASCII(ByVal input As String) As String
    Dim ASCIIList() As String = .....
    Dim BinaryList() As String = ......
    Dim BinarySubstrings = Enumerable.Range(0, input.Length \ 8).[Select](Function(i) input.Substring(i * 8, 8)).ToArray()
    Dim result = new List(Of String)()
    Dim binaryMatch As Integer

    For Each e As String In BinarySubstrings
        binaryMatch = Array.IndexOf(BinaryList, e)
        result.Add(ASCIIList(CInt(binaryMatch)))
    Next

    Return String.Join("", result.ToArray())
End Function