Value of type ‘List(Of String); cannot be converted to ‘String()’

I saw these 2 string examples on this link.

https://www.dotnetperls.com/convert-list-string-vbnet

I doing the first one using String.Join

I created a new page called Default.aspx and put a label called Label1 on the page

Then on this page Default.aspx.vb in the page load event I put this code.
Then when I run the page it works fine and the string is displayed on my label.

    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load

        ' Create list of three strings.
        Dim vals As List(Of String) = New List(Of String)
        vals.Add("dot")
        vals.Add("net")
        vals.Add("perls")

        ' Use string join function that receives IEnumerable.
        Dim value As String = String.Join(",", vals)

        'Show String On Label
        Label1.Text = value

    End Sub

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I have a .net 3.5 ASP.NET Web Forms application using VB.

In the page load event of my page I put the same code.

But I get this error message:


Any idea of why I'm getting this error message saying Listing(Of String) cannot be converted to String?