Merge two XElements

Question

I\'m not quite sure how to ask this, or if this even exists, but I have a need to merge two XElements with one taking precendence over the other, to become just one element.

Answer 1

Here's a console app that produces the result listed in your question. It uses recursion to process each sub element. The one thing it doesn't check for is child elements that appear in Elem2 that aren't in Elem1, but hopefully this will get you started towards a solution.

I'm not sure if I would say this is the best possible solution, but it does work.

Module Module1

Function MergeElements(ByVal Elem1 As XElement, ByVal Elem2 As XElement) As XElement

    If Elem2 Is Nothing Then
        Return Elem1
    End If

    Dim result = New XElement(Elem1.Name)

    For Each attr In Elem1.Attributes
        result.Add(attr)
    Next

    Dim Elem1AttributeNames = From attr In Elem1.Attributes _
                              Select attr.Name

    For Each attr In Elem2.Attributes
        If Not Elem1AttributeNames.Contains(attr.Name) Then
            result.Add(attr)
        End If
    Next

    If Elem1.Elements().Count > 0 Then
        For Each elem In Elem1.Elements
            result.Add(MergeElements(elem, Elem2.Element(elem.Name)))
        Next
    Else
        result.Value = Elem1.Value
    End If

    Return result
End Function

Sub Main()
    Dim Elem1 = 
                    Center
                    Gordie Howe
                

    Dim Elem2 = 
                    Wayne Gretzky
                

    Console.WriteLine(MergeElements(Elem1, Elem2))
    Console.ReadLine()
End Sub

End Module

Edit: I just noticed that the function was missing As XElement. I'm actually surprised that it worked without that! I work with VB.NET every day, but it has some quirks that I still don't totally understand.