How can I make a Property "ReadOnly" outside the Assembly (DLL) for people using the DLL but still be able to populate that property from within the assembly for them to read?

For example, if I have a Transaction object that needs to populate a property in a Document object (which is a child class of the Transaction class) when something happens in the Transaction object, but I just want to developer using my DLL to only be able to read that property and not change it (it should only be changed from within the DLL itself).

C#

public object MyProp {
   get { return val; }
   internal set { val = value; }
}

VB

Public Property MyProp As Object
   Get
      Return StoredVal
   End Get
   Friend Set(ByVal value As Object)
      StoredVal = value
   End Set
End Property

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