System.Xml.Serialization.TypeScope.GetEnumeratorElementType C# (CSharp) Method

        private static Type GetEnumeratorElementType(Type type, ref TypeFlags flags)
        {
            if (typeof(IEnumerable).IsAssignableFrom(type))
            {
                MethodInfo enumerator = type.GetMethod("GetEnumerator", new Type[0]);

                if (enumerator == null || !typeof(IEnumerator).IsAssignableFrom(enumerator.ReturnType))
                {
                    // try generic implementation
                    enumerator = null;
                    foreach (MemberInfo member in type.GetMember("System.Collections.Generic.IEnumerable<*", BindingFlags.Public | BindingFlags.Instance | BindingFlags.NonPublic))
                    {
                        enumerator = member as MethodInfo;
                        if (enumerator != null && typeof(IEnumerator).IsAssignableFrom(enumerator.ReturnType))
                        {
                            // use the first one we find
                            flags |= TypeFlags.GenericInterface;
                            break;
                        }
                        else
                        {
                            enumerator = null;
                        }
                    }
                    if (enumerator == null)
                    {
                        // and finally private interface implementation
                        flags |= TypeFlags.UsePrivateImplementation;
                        enumerator = type.GetMethod("System.Collections.IEnumerable.GetEnumerator", BindingFlags.Public | BindingFlags.Instance | BindingFlags.NonPublic, Array.Empty<Type>());
                    }
                }
                if (enumerator == null || !typeof(IEnumerator).IsAssignableFrom(enumerator.ReturnType))
                {
                    return null;
                }
                XmlAttributes methodAttrs = new XmlAttributes(enumerator);
                if (methodAttrs.XmlIgnore) return null;

                PropertyInfo p = enumerator.ReturnType.GetProperty("Current");
                Type currentType = (p == null ? typeof(object) : p.PropertyType);

                MethodInfo addMethod = type.GetMethod("Add", new Type[] { currentType });

                if (addMethod == null && currentType != typeof(object))
                {
                    currentType = typeof(object);
                    addMethod = type.GetMethod("Add", new Type[] { currentType });
                }
                if (addMethod == null)
                {
                    throw new InvalidOperationException(SR.Format(SR.XmlNoAddMethod, type.FullName, currentType, "IEnumerable"));
                }
                return currentType;
            }
            else
            {
                return null;
            }
        }