IsNull Always Returns True

Question

The function IsNull(char) in my below code is always returning true. Why?

StrText is getting it from a text field and the value is:

strText = +  96666

The particular section that is giving me an issue:

 If intCounter = 1 And strChar = "+" Then
            For Count = intCounter + 1 To Len(strText)
                Char = Mid(strText, Count, 1)
                If IsNull(Char) = True Then
                    Count = Count + 1
                End If
                If IsNumeric(Char) And Char <> "0" Then
                    Exit For
                    MsgBox "Problem"
                End If
            Next Count
        End If

the complete function is:

Public Function NumbersOnly(ByVal strText As String) As Boolean
    Dim intCounter As Integer
    Dim strChar As String
    Dim Count As Integer
    Dim Char As String
    strText = Trim(strText)
    For intCounter = 1 To Len(strText)
        strChar = Mid(strText, intCounter, 1)
        If intCounter = 1 And IsNumeric(strChar) = False And strChar <> "+" Then
            NumbersOnly = False
            Exit Function
        End If
        If intCounter = 1 And strChar = "+" Then
            For Count = intCounter + 1 To Len(strText)
                Char = Mid(strText, Count, 1)
                If IsNull(Char) = True Then
                    Count = Count + 1
                End If
                If IsNumeric(Char) And Char <> "0" Then
                    Exit For
                    MsgBox "Problem"
                End If
            Next Count
        End If
        If intCounter <> 1 And (IsNumeric(strChar) = False And strChar <> " ") Then
            NumbersOnly = False
            Exit Function
        End If
    Next intCounter
    NumbersOnly = True
End Function

Answer 1

Strings are initialized to an empty string, not null or nothing.

Consider the following subroutine:

Sub test()
    Dim char As String

    If IsNull(char) Then
        Debug.Print "I can't get here."
    ElseIf char = "" Then
        Debug.Print "HELLO THERE!"
    End If

    char = "sometext"
    If IsNull(char) Then
        Debug.Print "I can't get here."
    ElseIf char = "" Then
        Debug.Print "Now this fails too"
    Else
        Debug.Print "Hello Again."
    End If
End Sub

In short, you don't want to check to see if your char variable is null, you want to check to see if it's an empty string.