VB.Net - Tips on creating a function library - Shared function? No instancing!

[BitFlipper88]

Hi,

I am simply trying to create a library of common functions I've written. I used the 'Class Library' template project.

But I'm running into issues with member accessibility. Because I DON'T want to instance this library, as its purely a namespace, I was making class members (functions) 'SHARED' for the time being (for testing).
But this can't be the way a namespace is written. Now I have problems accessing private members in the class from within a shared function.

What is the way to approach this?

Namespace CustomFunctions

    Public Class Str  'there are mutliple classes within this namespace to organize the entire library

        Shared Function HasAlpha(ByVal Str As String) As Boolean
            'check for alphabetic characters
            For i = 0 To Str.Length - 1
                If Char.IsLetter(Str.Chars(i)) Then
                    Return True
                End If
            Next
            Return False
        End Function
        Shared Function IsNumeric(ByVal Str As String) As Boolean
            'check if only numbers
            For i = 0 To Str.Length - 1
                If Not Char.IsNumber(Str.Chars(i)) Then
                    Return False
                End If
            Next
            Return True
        End Function

        Shared Function CountChar(Str As String, Character As String) As Integer
            'count characters in string
            Dim count As Long
            For Each c As Char In Str
                If c = Character Then
                    count = count + 1
                End If
            Next
            Return count
        End Function

    End Class
End Namespace

[techgnome]

Namespaces are simply a logical organization tool for classes. You don't "write a namespace"...

As for the shared functions .... yep, that's the way you do it. You create a class and put in functions... private, public, or shared. Sounds like shared is what you want.
As for accessing private variables, you shouldn't have problems. Except that you swerved when comes to your parameters... you gave them the same name as your class. So when you do Str.Char ... it doesn't know what Str you're referring to. You'e ocnfusedit.

Give your functios meaningful names ... StringToCount, CharCount, CharToCount, SringToCheck. StrToCheck, Str2Chk...


-tg

[BitFlipper88]

Hi Thanks for the tips.

I didn't catch that my class name conflicted with my input parameters. Fixed.
As for semantics: you don't write classes either, they're just a logical organization tool for code.

Nevertheless, I am still having issues trying to access a private member from a shared function without instantiating the object. As described in the code below:

Namespace CustomFunctions

    Public Class StringFunctions
        Shared Function HasAlpha(ByVal Str As String) As Boolean
            'check for alphabetic characters
            For i = 0 To Str.Length - 1
                If Char.IsLetter(Str.Chars(i)) Then
                    Return True
                End If
            Next
            Return False
        End Function
        Shared Function IsNumeric(ByVal Str As String) As Boolean
            'check if only numbers
            For i = 0 To Str.Length - 1
                If Not Char.IsNumber(Str.Chars(i)) Then
                    Return False
                End If
            Next
            Return True

        End Function

        Shared Function CountChar(Str As String, Character As String) As Integer
            'count characters in string
            Dim count As Long
            For Each c As Char In Str
                If c = Character Then
                    count = count + 1
                End If
            Next
            Return count
        End Function

        Shared Function Test_The_Test() As String
            Return Test("Hello World")  'not allowed without an instance of the class?
        End Function


        Private Function Test(InputString As String) As String
            Return InputString
        End Function

    End Class
End Namespace

Exception:

Error	BC30369	Cannot refer to an instance member of a class from within a shared method or shared member initializer without an explicit instance of the class.

[OptionBase1]

Should be:

Private Shared Function Test

I believe pretty much everything accessed as a non-instance needs to be "Shared", which doesn't imply that it is externally visible.

From https://learn.microsoft.com/en-us/do...difiers/shared :

"Sharing does not alter the access level of a member. For example, a class member can be shared and private (accessible only from within the class), or non-shared and public."

[BitFlipper88]

Hi,

Yes. I just realized this. I wasn't aware a function could be shared and private. Great!

[Shaggy Hiker]

If this is all in a class library, you might want to use Friend rather than Private. Friend is public...but only in the same assembly, which means just in the class library, in this case.