C# XML Serialize without a wrapper

Question

I have the following class fragment:

public class varString
{
    public string KeyWord;
    public string Value;
    public static implicit operator string(varString v)
    {
        return v == null ? null : (string)v.Value;
    }
}

KeyWord is allowed to be null.

When serializing to XML, I get the following output when KeyWord is null:

<varString>
    <Value>value goes here</Value>
</varString>

How can I get the XML serializer to output the following when and only when KeyWord is null?:

<varString>value goes here</varString>

If KeyWord is not null, I'd still like it to output the following:

<varString>
    <!-- Can either be <Value></Value or just straight text -->
    <KeyWord>KeyWord goes here</KeyWord>
<varString>

Please note that I have already modified the deserialize events to handle this case to convert the lone string into a varString with a null KeyWord.

Why do you need that? It makes the xml harder to parse for the receipent. — L.B
– L.B, Commented Nov 2, 2016 at 19:53
It's easier for me to edit the xml in this way. KeyWord is 9/10 times null, so I'd rather not have the extra tag output. Just personal preference is all, doesn't really affect anything. — Polosky
– Polosky, Commented Nov 2, 2016 at 20:10

dbc · Accepted Answer · 2016-11-02 20:12:46Z

1

Mark Value with the attribute [XmlText]:

public class varString
{
    [XmlText]
    public string Value;
    public string KeyWord;
    public static implicit operator string(varString v)
    {
        return v == null ? null : (string)v.Value;
    }
}

Sample fiddle.

answered Nov 2, 2016 at 20:12

dbc

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4 Comments

Polosky Over a year ago

This works in the fiddle, but I can't seem to get it to work with a more complex object that contains these in my code. However, I think this is the easiest and simplest solution so I'm marking it as the answer because it does work.

dbc Over a year ago

@Hondros - Check the Remarks section of the docs, e.g. Only one instance of the XmlTextAttribute class can be applied in a class. and You can apply the XmlTextAttribute to public fields and public read/write properties that return primitive and enumeration types.

Polosky Over a year ago

Hm interesting. I modified your fiddle to see if it would support classes with defined varStrings: dotnetfiddle.net/yan3ts . And it does in fact work. I'm sure I can figure it out from here though. Thanks so much!

Polosky Over a year ago

I figured it out. I'm running a converter on some of my xml files, so the input was expecting XmlText even though <value> tags are currently there, so they weren't being read in.

Alexander Petrov · Accepted Answer · 2016-11-02 20:15:53Z

0

Try this approach:

var vs = new varString();
vs.KeyWord = "key"; // null;
vs.Value = "value";


var attr = new XmlAttributes();

if (vs.KeyWord == null)
    attr.XmlText = new XmlTextAttribute();
else
    attr.XmlElements.Add(new XmlElementAttribute { ElementName = "Value" });

var overrides = new XmlAttributeOverrides();
overrides.Add(typeof(varString), "Value", attr);


var xs = new XmlSerializer(typeof(varString), overrides);
xs.Serialize(Console.Out, vs);

Depending on the KeyWord value we add XmlTextAttribute or XmlElementAttribute.

answered Nov 2, 2016 at 20:15

Alexander Petrov

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3 Comments

Polosky Over a year ago

Unfortunately, I don't think this will work for me because each varString would have a null keyword on a case by case basis, and I am using a container class to hold multiple varStrings.

Alexander Petrov Over a year ago

@Hondros - Yes, for multiple values it's inapplicable.

dbc Over a year ago

You need to cache the serializer if you construct it using XmlAttributeOverrides. See Memory Leak using StreamReader and XmlSerializer

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