AutoCAD .NET :: Slowing Down When Changing Block Reference Property Values

I'm inserting automatically many references to a couple of dynamic blocks in an AutoCAD drawing using VB.NET. If the number of inserted references is not very big, it works fine but, if I´m inserting hundreds of them, I noticed the app is slowing down a lot.

After taking some measures of the time the app uses in its execution, I noticed changing the value of the block reference property is slower as the number of inserted block increases: it takes 10 or 20 miliseconds at the begining but it can take more than 1 second after inserting one thousand of block references (to the same block).This is the function I use to change the property values:

Protected Sub CambiarPropiedades(ByRef ed As Editor, _ ByRef br As BlockReference, _ByVal nombrePropiedad As String, _ ByVal valor As Double) Dim pc As DynamicBlockReferencePropertyCollection = br.DynamicBlockReferencePropertyCollection If br IsNot Nothing And br.IsDynamicBlock Then For Each prop As DynamicBlockReferenceProperty In pc If prop.PropertyName = nombrePropiedad Then prop.Value = valor '

This line takes a long time the first time I call this function for the ' same block reference but it is faster in the next calls . It also changes the block reference name (br.name) in the first call

Exit For End If Next End If End Sub.

Which I call to change all the properties I need to change in an inserted block reference:

CambiarPropiedades(ed, br, "h_testua", objElementoLaboratorio.POS_TEXTO) CambiarPropiedades(ed, br, "d_texto_hor", posxTexto) CambiarPropiedades(ed, br, "largo", objElementoLaboratorio.LARGO) CambiarPropiedades(ed, br, "fondo", objElementoLaboratorio.FONDO)
 A weird thing I noticed is that when I call this function to change the first property of an inserted block, it also changes the .Name of the block reference.

Even if I change the order in the property modification, it takes always a lot in the first call, it does not depend on the property I´m changing.