ASP.NET what is [datamember] [datacontract] in class giving errors
<p>Im following a guide which tell me to create a simple class file and add following code</p>

<pre><code>[DataContract]
</code></pre>

<p>public class Footballers
{
    [DataMember]
    public string FirstName { get; set; }</p>

<pre><code>[DataMember]
public string LastName { get; set; }

[DataMember]
public DateTime BirthDate { get; set; }
</code></pre>

<p>}</p>

<p>I get an error around [datacontract] and [datamember] saying type or namespace can not be found. </p>

<p>Firstly I guess what namespace do Need to include ?
Secondly are these things necessary ?
Lastly what do they do, I have never seen them in a class file before ?</p>
