how about a WCF service to query the SQL database and build the point geometries?
http://blogs.esri.com/Dev/blogs/silverlightwpf/archive/2010/03/11/Sending-geometry-between-Silverlig...
lance
take=100;
skip=0;
for (int i = 0; i < 20000; i++)
{
var results = ServiceContext.GetLocations(skip, take);
results.Completed += Results_Completed;
skip = skip + take;
}
private void Results_Completed(object sender, System.EventArgs e)
{
}