"Remove is an Invalid Operation" && Insertis an Invalid Operation

Hi,

I have read on many posts about the error message that it is there because we try to write to a collection when it is in ReadOnly mode.

In my case I am setting a property and after that using PropertyHasChanged(string item) method

where the error comes.

The class in which we have used the validation is inheritted from BusinessBAse.

I would like to know where is the best place to set ReadOnlyP propert to False and 

which method shoul I implement and if you can let me know how.

I would appreciate,

Thanks in advance.