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PO.NET XmlSerializer and nested classes in C#
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copied!<p>I have encountered some surprising behavior using XmlSerializer in C#. Consider the following piece of code.</p> <pre><code>public class A : IEnumerable { public class B { [XmlAttribute] public string PropA { get; set; } [XmlElement] public string PropB { get; set; } } public IEnumerator GetEnumerator () { yield break; } } class Program { static void Main (string[] args) { XmlSerializer serializer = new XmlSerializer(typeof(A.B)); XmlTextWriter writer = new XmlTextWriter(@"E:\temp\test.xml", Encoding.Default); serializer.Serialize(writer, new A.B() { PropA = "one", PropB = "two" }); } } </code></pre> <p>In this example I try to serialize an instance of nested class A.B, which itself doesn't make use of the container class A in any way. But when I attempt to construct the XmlSerializer for it, the following exception is thrown:</p> <blockquote> <p>InvalidOperationException was unhandled:</p> <p>To be XML serializable, types which inherit from IEnumerable must have an implementation of Add(System.Object) at all levels of their inheritance hierarchy. Test.A does not implement Add(System.Object).</p> </blockquote> <p>XmlSerializer is trying to apply serialization constraints against type A when I'm actually trying to serialize type A.B. My understanding however is that aside from privileged access to data in instances of the outer type, a nested type is not special and behaves as if it were in a namespace. </p> <p>Is this understanding incorrect, and <strong>do the semantics of nested types or XmlSerializer justify this behavior, or does this feel like a bug in XmlSerializer?</strong></p> <p>In specific regard to XmlSerializer semantics, is there any documented requirement that enforces XmlSerializer constraints on all outer types when applied against a nested type?</p>

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