Esto es lo que me ocurrió, para aquellos que son curiosos:
Imports System.Runtime.CompilerServices
Module sbExtension
<Extension()> _
Public Sub AppendFormattedLine(ByVal oStr As System.Text.StringBuilder, _
ByVal format As String, _
ByVal arg0 As Object)
oStr.AppendFormat("{0}{1}", String.Format(format, arg0), ControlChars.NewLine)
End Sub
<Extension()> _
Public Sub AppendFormattedLine(ByVal oStr As System.Text.StringBuilder, _
ByVal format As String, ByVal arg0 As Object, _
ByVal arg1 As Object)
oStr.AppendFormat("{0}{1}", String.Format(format, arg0, arg1), ControlChars.NewLine)
End Sub
<Extension()> _
Public Sub AppendFormattedLine(ByVal oStr As System.Text.StringBuilder, _
ByVal format As String, _
ByVal arg0 As Object, _
ByVal arg1 As Object, _
ByVal arg2 As Object)
oStr.AppendFormat("{0}{1}", String.Format(format, arg0, arg1, arg2), ControlChars.NewLine)
End Sub
<Extension()> _
Public Sub AppendFormattedLine(ByVal oStr As System.Text.StringBuilder, _
ByVal format As String, _
ByVal ParamArray args() As Object)
oStr.AppendFormat("{0}{1}", String.Format(format, args), ControlChars.NewLine)
End Sub
End Module
¿Alguien sabe por qué está sellado? – oleks
@oleks: Probablemente porque cuesta dinero probar y validar las API y su sellado reduce este costo. –