Chaining overloaded constructors

I am trying to create an efficient class with minimum code-duplication.

I have this defined:

Public Class Foo
    Private _firstName as string = ""
    Private _lastName as string = ""

    Public Sub New(ByVal userGUID As Guid)
        'query DB to get firstName and lastName
        Me.New(dt.Rows(0)("FirstName").ToString(),dt.Rows(0)("LastName").ToString())
    End Sub

    Public Sub New(ByVal firstName As String, ByVal lastName As String)
        _firstName = firstName.toUpper()
        _lastName = lastName.toUpper()
        Validate()
    End Sub

    Private Sub Validate()
        ' Throw error if something is wrong
    End Sub
End Class

The Constructor with firstName and lastName parameters is the end-point constructor that does validation. A constructor with userGUID as a parameter would query DB to obtain name and call the final constructor. This way all execution should be directed towards one of the constructors that actually does all validation etc etc. The idea behind it is that if I add new contructors, I only have to pull necessary data (firstname/lastname) and call the final constructor that does validation.

However, there is a compilation error preventing me from using this system on line Me.New(dt.Rows(0)("FirstName").ToString(),dt.Rows(0)("LastName").ToString()). Apparently this line has to be the first line in the constructor. But If I have this as first line, it will break the validation process because validation will throw an error due to no firstname/lastname. I have to query the DB in order to pull that info.

I am aware that I can assign values here and call validation from this constructor too, but this will effectively isolate this constructor from the final one, thus duplicating code and adding to maintenance a bit. FYI, in the example below I only have 2 constructors, but in reality i have several more. If each will do its own assignment it just adds up to maintenance that much.

So, is there a way to achieve my task by executing some code and THEN calling an overloaded constructor?

Thank you for any insight