Solve String Equations

Module LHMath
    Private setNumbers As Char() = {"0", "1", "2", "3", "4", "5", "6", "7", "8", "9", "."}
    Private setMath As Char() = {"*", "/", "+", "-"}
 
    Private Function chrCount(ByVal src As String, ByVal chr As Char) As Int32
        Dim total As Int32 = 0
        Dim chrSrc As Char() = src.ToCharArray
        For i As Integer = 0 To chrSrc.Length - 1
            If (chrSrc(i) = chr) Then
                total += 1
            End If
        Next
        Return total
    End Function
 
    Private Function aChrContains(ByVal src As Char(), ByVal chr As Char) As Boolean
        For I As Integer = 0 To src.Length - 1
            If (src(I) = chr) Then
                Return True
            End If
        Next
        Return False
    End Function
 
    Private Function aStrContains(ByVal src As Char(), ByVal str As String) As Boolean
        Dim chrStr As Char() = str.ToCharArray
        For I As Integer = 0 To chrStr.Length - 1
            If (aChrContains(src, chrStr(I)) = True) Then
                Return True
            End If
        Next
        Return False
    End Function
 
    Private Function SolveSingleEquation(ByVal obj1 As String, ByVal obj2 As String, ByVal symbol As String) As Double
        obj1 = obj1.Replace(" ", "")
        obj2 = obj2.Replace(" ", "")
        symbol = symbol.Replace(" ", "")
        Select Case symbol
            Case "*"
                Return CDec(obj1) * CDec(obj2)
            Case "/"
                Return CDec(obj1) / CDec(obj2)
            Case "+"
                Return CDec(obj1) + CDec(obj2)
            Case "-"
                Return CDec(obj1) - CDec(obj2)
        End Select
        Return 0
    End Function
 
    Private Function GetEquationNotation(ByVal src As String) As String()
        Dim Equ As String = src.Replace(" ", "")
        Dim chrEqu As Char() = Eq*****CharArray
        Dim MyStack As New List(Of String)
        Dim Temp As String = Nothing
        For I As Integer = 0 To chrEqu.Length - 1
            If (aChrContains(setMath, chrEqu(I))) Then
                If Not (Temp = "") Then
                    MyStack.Add(Temp)
                Else
                    MyStack.Add("0")
                End If
                MyStack.Add(chrEqu(I))
                Temp = ""
            ElseIf (I = chrEqu.Length - 1) Then
                Temp = Temp & chrEqu(I)
                MyStack.Add(Temp)
                Temp = ""
            ElseIf (Char.IsLetterOrDigit(chrEqu(I))) Then
                Temp = Temp & chrEqu(I)
            End If
        Next
        Return MyStack.ToArray
    End Function
 
    Private Function SolveSimpleEquation(ByVal NT As String()) As String
        If (NT.Length = 0) Then
            Return "0"
        ElseIf (NT.Length = 1) Then
            Return NT(0)
        ElseIf (NT.Length = 2) Then
            Return "0"
        End If
        Dim ToBeCalculated As String = Nothing
        Dim A, B, C As String
        A = ""
        B = ""
        C = ""
        For I As Integer = 0 To NT.Length - 1
            If (A = "") Then
                A = NT(I)
            ElseIf (B = "") Then
                B = NT(I)
            ElseIf (C = "") Then
                C = NT(I)
            Else
                If (B = "*" Or B = "/") Then
                    A = SolveSingleEquation(A, C, B).ToString
                    B = NT(I)
                    C = ""
                ElseIf (NT(I) = "*" Or NT(I) = "/") Then
                    ToBeCalculated = ToBeCalculated & A & B
                    A = C
                    B = NT(I)
                    C = ""
                ElseIf (NT(I) = "+" Or NT(I) = "-") Then
                    A = SolveSingleEquation(A, C, B).ToString
                    B = NT(I)
                    C = ""
                End If
            End If
        Next
        A = SolveSingleEquation(A, C, B).ToString
        If (ToBeCalculated = "") Then
            Return A
        Else
            Dim Remains As String = ToBeCalculated & A
            Dim rNT As String() = GetEquationNotation(Remains)
            A = SolveSimpleEquation(rNT)
            Return A
        End If
        Return 0
    End Function
 
    Private Function SolveComplexEquation(ByVal src As String) As Double
        Dim Equ As String = src.Replace(" ", "")
        While (Equ.Contains("("))
            Dim A, B, C As String
            A = ""
            B = ""
            C = ""
            Dim splParam As String() = Equ.Split("(")
            For I As Integer = 0 To splParam.Length - 2
                A = A & splParam(I)
            Next
            Dim sprParam As String() = splParam(splParam.Length - 1).Split(")")
            For I As Integer = 1 To sprParam.Length - 1
                C = C & sprParam(I)
            Next
            Dim splitEqu As String = splParam(splParam.Length - 1).Split(")")(0)
            Dim tNT As String() = GetEquationNotation(splitEqu)
            B = SolveSimpleEquation(tNT)
            Equ = A & B & C
        End While
        Dim fNT As String() = GetEquationNotation(Equ)
        Dim Answer As String = SolveSimpleEquation(fNT)
        Return Answer
    End Function
 
    Public Function SolveEquation(ByVal src As String) As Decimal
        Return SolveComplexEquation(src)
    End Function
End Module