System.Runtime.Serialization.DataContractSet.GetReferencedTypes C# (CSharp) Method

        private Dictionary<XmlQualifiedName, object> GetReferencedTypes()
        {
            if (_referencedTypesDictionary == null)
            {
                _referencedTypesDictionary = new Dictionary<XmlQualifiedName, object>();
                //Always include Nullable as referenced type
                //Do not allow surrogating Nullable<T>
                _referencedTypesDictionary.Add(DataContract.GetStableName(Globals.TypeOfNullable), Globals.TypeOfNullable);
                if (_referencedTypes != null)
                {
                    foreach (Type type in _referencedTypes)
                    {
                        if (type == null)
                            throw DiagnosticUtility.ExceptionUtility.ThrowHelperError(new InvalidOperationException(SR.Format(SR.ReferencedTypesCannotContainNull)));

                        AddReferencedType(_referencedTypesDictionary, type);
                    }
                }
            }
            return _referencedTypesDictionary;
        }