I have seen several post detailing how to get around the ReadOnly barrier in adding connection strings to ConfigurationManager.ConnectionStrings. See an example of one such post below. Along of each of these examples comes a dire, yet vague warning that the technique employed is "dangerous". What is the danger?
Dim cssc As ConnectionStringSettingsCollection = WebConfigurationManager.ConnectionStrings
Dim t As Type = cssc.GetType().BaseType ' System.Configuration.ConfigurationElementCollection
Dim fi As FieldInfo = t.GetField("bReadOnly", BindingFlags.Instance Or BindingFlags.NonPublic)
fi.SetValue(cssc, False)