Validation against XSD with different namespace

Question

I have an XML file and an XSD file that may have the wrong namespace if someone has put the wrong version in the validation folder.  When the file is the correct version, then the validator works fine, and lists all errors in the XML, but when wrong, just reports the XML as valid.

I'm using the following code..

Dim errors As Boolean = False
Dim FullErrors As String = ""
Private Sub XSDErrors(ByVal o As Object, ByVal e As ValidationEventArgs)
    FullErrors += Regex.Replace(e.Message, "http:.*:", "") + Environment.NewLine
    errors = True
End Sub

Private Sub btnValidateXML_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnValidateXML.Click
    Dim schemas As XmlSchemaSet = New XmlSchemaSet()
    Dim XMLDoc As New XDocument()

    Try
        XMLDoc = XDocument.Parse(txtXML.Text)
    Catch ex As Exception
        txtXMLErrors.Text = "This is not a well formed XML document"
        Return
    End Try
    schemas.Add(Nothing, "exb.xsd")

    errors = False
    FullErrors = ""
    XMLDoc.Validate(schemas, AddressOf XSDErrors)

    If errors Then
        txtXMLErrors.Text = FullErrors
    Else
        txtXMLErrors.Text = "Validation Successful"
    End If
End Sub

How can you check that the namespace of the XML and XSD documents match before doing the validation?