Convert Dictionary into structured format string

I would have written the whole method block with Linq like this (sorry for the C#-vb.net soup...)

c-sharp

return String.Join(",",Me._set.Select(kvp=>String.Format("{0}={1}",kvp.Key, kvp.Value).ToArray());

Also, I don't really know what _set is. Maybe you'll have to cast :

c-sharp:

return String.Join(",", Me._set.Cast<KeyValuePair<String,String>>().Select(kvp=>String.Format("{0}={1}",kvp.Key, kvp.Value).ToArray());

vb.net:

return String.Join(", ", Me.Select(Function(kvp) String.Format("{0}={1}", kvp.Key, kvp.Value)).ToArray())

Hope this will help,

VB.net syntax:

Dim dic As New Dictionary(Of String, String)() From {
            {"a", "1"},
            {"b", "2"},
            {"c", "3"},
            {"d", "4"}
            }

Dim s As String = String.Join(",", dic.Select(Function(pair) String.Format("{0}={1}", pair.Key, pair.Value)).ToArray())

As far as your non-LINQ loop goes, I would recommend doing it like this:

Public Overrides Function ToString() As String
    Dim items As New List(Of String)(_set.Count)
    For Each pair As KeyValuePair(Of String, String) In _set
        items.Add($"{pair.Key}={pair.Value}"))
    Next
    Return String.Join(", ", items)
End Function

With LINQ, you could do it like this:

Public Overrides Function ToString() As String
    Return String.Join(", ", _set.Select(Function(pair) $"{pair.Key}={pair.Value}"))
End Function