I have a class containing an array I wish to serialize with XmlSerializer:
[XmlArray("properties")]
[XmlArrayItem("property", IsNullable = true)]
public List<Property> Properties { get; set; }
Property
is a class containing an attribute and some XmlText
:
[XmlAttribute("name")]
public string Name { get; set; }
[XmlText]
public string Value { get; set; }
The problem is that when Value
is null, it serializes as an empty string:
<property name="foo" />
rather than a null. I'm looking for the value to either be omitted entirely, or look like this:
<property name="foo" xsi:nil="true" />
Is it possible to null out an element in a list based on its XmlText
value? I'm really trying to avoid custom serialization, but perhaps some other serialization framework would be better in this case?
Use the IsNullable=true in the XmlArrayItemAttribute class. For an example.
[XmlRoot("Root")]
public class Root
{
[XmlArrayItem("Element", IsNullable = true)]
public string[] Elements { get; set; }
}
Some sample code in Visual Studion 2012 and .Net 4.5:
using System.Xml.Serialization;
...
// Test object
Root root;
root = new Root();
root.Elements = new string[] { null, "abc" };
using(MemoryStream stream = new MemoryStream())
{
XmlSerializer xmlSerializer = new XmlSerializer(typeof(Root));
xmlSerializer.Serialize(stream, root);
Console.WriteLine(new string(Encoding.UTF8.GetChars(stream.GetBuffer())));
}
The output is (line breaks added for clarity):
<?xml version="1.0"?>
<Root
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:xsd="http://www.w3.org/2001/XMLSchema">
<Element>
<string xsi:nil="true" />
<string>abc</string>
</Element>
</Root>
And with a complex type (also in .Net 4.5 on Visual Studio 2012):
public class MyProperty
{
public string Foo { get; set; }
}
[XmlRoot("Root")]
public class Root
{
[XmlArrayItem("Element", IsNullable = true)]
public MyProperty[] Elements { get; set; }
}
,,,
Root root;
root = new Root();
root.Elements = new MyProperty[] { null, new MyProperty{ Foo = "bar" } };
// Other code is as above
Using the same code above produces:
<?xml version="1.0"?>
<Root
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:xsd="http://www.w3.org/2001/XMLSchema">
<Elements>
<Element xsi:nil="true" />
<Element>
<Foo>bar</Foo>
</Element>
</Elements>
</Root>
Also remember that the type must be a reference type (not a struct, for example) to write out xsi:nil=true
.
One thought - you could use "NameSpecified", but check the value of "Value" in the get. Meaning, if Value is null, then Name will not be output either.
Unfortunately, you will still have a null property xml element, tho; I hope that's more acceptable...
class Program
{
static void Main(string[] args)
{
ObjectWithProperties obj = new ObjectWithProperties()
{
Properties = new List<Property>()
};
Property p = new Property();
p.Name = "This WILL Show Up";
p.Value = "I'm here";
obj.Properties.Add(p);
Property p1 = new Property();
p1.Name = "This Will NOT Show Up";
obj.Properties.Add(p1);
Console.WriteLine(ToXmlString(obj));
Console.ReadLine();
}
public static string ToXmlString(object value)
{
if (value == null) return string.Empty;
XmlSerializer ser = new XmlSerializer(value.GetType());
MemoryStream ms = new MemoryStream();
ser.Serialize(ms, value);
return Encoding.UTF8.GetString(ms.ToArray());
}
}
public class ObjectWithProperties
{
[XmlArray("properties")]
[XmlArrayItem("property", IsNullable = true)]
public List<Property> Properties { get; set; }
}
public class Property
{
[XmlAttribute("name")]
public string Name { get; set; }
[XmlIgnore]
public bool NameSpecified
{
get { return !string.IsNullOrEmpty(Value); }
}
[XmlText]
public string Value { get; set; }
}
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