Question

I am having trouble understanding the difference between these two commands that in my mind should do the same thing. I have posted the entire code below in case anything is unclear.

I have created two functions in class Person, one that returns a list containing first,middle and last names and one that returns a concatenated string of the name. I reference the function that returns the list to concatenate the string with the line below:

FullName = String.Join(" ", Me.Get_NameList())

However, when I call:

Console.WriteLine(Person1.Print_Name())

I get what looks like the list object instead of the string:

System.Collections.Generic.List`1[System.String]

If I change the code to look like this:

    Public Function Print_Name()
        Dim FullNameList As List(Of String) = Me.Get_NameList()
        Dim FullName As String
        FullName = String.Join(" ", FullNameList)
        Return FullName
    End Function

The console prints:

John Q Doe

Why am I getting a different answer by first assigning the list to a variable and then joining it? Does this have something to do with how the list is stored in memory?

Thanks in advance for the help.

Here is the full code:

Imports System
Module Module1
    Sub Main()
        Dim Person1 As New Person("John", "Q", "Doe")
        Console.WriteLine("Get_Name Values")
        Dim g1 As List(Of String) = Person1.Get_NameList()
        Console.WriteLine(String.Join(" ", g1))
        Console.WriteLine("Print_Name Values")
        Console.WriteLine(Person1.Print_Name())
    End Sub
End Module

Class Person
    Private FirstName As String
    Private MiddleName As String
    Private LastName As String
    Public Sub New(ByVal Fn As String, ByVal Mn As String, ByVal Ln As String)
        FirstName = Fn
        MiddleName = Mn
        LastName = Ln
    End Sub
    Public Function Get_NameList()
        Dim NameList As New List(Of String)
        NameList.Add(FirstName)
        NameList.Add(MiddleName)
        NameList.Add(LastName)
        Return NameList
    End Function
    Public Function Print_Name()
        'Dim FullNameList As List(Of String) = Me.Get_NameList()
        Dim FullName As String
        FullName = String.Join(" ", Me.Get_NameList())
        Return FullName
    End Function
End Class

Answer 1

GetNameList returns an Object (because you don’t specify the return type).

So the Join method is getting an object. So the VB.Net is turning the Object into a String() with one element that is Object.ToString(). Sometimes the method, especially if it is an old school VB holdover, would check to see if the object passed was an IEnumerable and just iterate over the Objects in the passed object. But not always. So having Strict and Explicit OFF can lead to very strange and hard to find bugs. Those two things should only be OFF in very specific cases where you want all the flexibility turning them off gives you AND you are ready to deal with the oddities that result.

Change the return type of Get_NameList to List(Of String)

And turn on option Strict ON and Option Explicit On to see your other problems.