Hide Empty String Property In WCF Serializing

We hide an empty string-property by serializing with EmitDefaultValue.

Introduction

In this tip, I will show you a trick: how you can hide a string-type property in the serialized XML if it is empty. Empty but not null!

Background

Normally, if you use EmitDefaultValue = false on a string property, DataContractSerializer will ignore this property if it has its default value. String has the default value = null. An empty string will be serialized like e.g. <Title></Title>.

You can save a huge amount of characters, if these empty properties will be simply ignored. If in your application, it has no special meaning, if a string property is null or is empty, you can use this trick to hide empty string values.

How to do it

We make a private property, which will be used only for the transfer.

/// <summary>
/// This property will be used only for transfer
/// </summary>
[DataMember(EmitDefaultValue = false, Name = "Title")]
private string TitleTransfer { get; set; }

It is private, but for the DataContractSerializer it is no problem. The original property will be decorated with IgnoreDataMember, so it will not be transported.

/// <summary>
/// Title of the person.
/// It can be empty.
/// </summary>
[IgnoreDataMember]
public string Title
{
    get { return this.TitleTransfer ?? string.Empty; }
    set
    {
        this.TitleTransfer = String.IsNullOrEmpty(value) ? null : value;
    }
}

In the setter of the original property, I set the transfer-property to null, if the value would be empty. So the transfer-property will never be empty but null.

Test it! 

var p1 = new Person() { Title = "Prof.", ForeName = "Albert", LastName = "Einstein" };

So a Person with Title will be serialized as usual.

<Person xmlns:i="http://www.w3.org/2001/XMLSchema-instance" xmlns="...">
  <ForeName>Albert</ForeName>
  <LastName>Einstein</LastName>
  <Title>Prof.</Title>
</Person>

But a Person without Title (empty)...

var p2 = new Person() { Title = string.Empty, ForeName = "Laszlo", LastName = "Vörös" };

... will be serialized like this:

<Person xmlns:i="http://www.w3.org/2001/XMLSchema-instance" xmlns="...">
  <ForeName>Laszlo</ForeName>
  <LastName>Vörös</LastName>
</Person>