c# - streaming XML serialization in .net

Question

I'm trying to serialize a very large IEnumerable<MyObject> using an XmlSerializer without keeping all the objects in memory.

The IEnumerable<MyObject> is actually lazy..

I'm looking for a streaming solution that will:

1. Take an object from the IEnumerable<MyObject> Serialize it to the underlying stream using the standard serialization (I don't want to handcraft the XML here!)
2. Discard the in memory data and move to the next

I'm trying with this code:

using (var writer = new StreamWriter(filePath))
{
 var xmlSerializer = new XmlSerializer(typeof(MyObject));
  foreach (var myObject in myObjectsIEnumerable)
  {
   xmlSerializer.Serialize(writer, myObject);
  }
}

but I'm getting multiple XML headers and I cannot specify a root tag <MyObjects> so my XML is invalid.

Any idea?

Thanks

Answer 1

The XmlWriter class is a fast streaming API for XML generation. It is rather low-level, MSDN has an article on instantiating a validating XmlWriter using XmlWriter.Create().

Edit: link fixed. Here is sample code from the article:

async Task TestWriter(Stream stream) 
{
    XmlWriterSettings settings = new XmlWriterSettings();
    settings.Async = true;

    using (XmlWriter writer = XmlWriter.Create(stream, settings)) {
        await writer.WriteStartElementAsync("pf", "root", "http://ns");
        await writer.WriteStartElementAsync(null, "sub", null);
        await writer.WriteAttributeStringAsync(null, "att", null, "val");
        await writer.WriteStringAsync("text");
        await writer.WriteEndElementAsync();
        await writer.WriteCommentAsync("cValue");
        await writer.WriteCDataAsync("cdata value");
        await writer.WriteEndElementAsync();
        await writer.FlushAsync();
    }
}