How force a maximum string length in a C# web service object property?

public class Person
{
     public string FirstName { get; set; }
     public string LastName { get; set; }
}

[ValidationSchema("person.xsd")]
public class Person { /* ... */ }

<!-- person.xsd -->

<?xml version="1.0"?>
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema">

  <xsd:element name="Person" type="PersonType" />

  <xsd:simpleType name="NameString">
     <xsd:restriction base="xsd:string">
        <xsd:maxLength value="255"/>
     </xsd:restriction>
  </xsd:simpleType>

  <xsd:complexType name="PersonType">
    <xsd:sequence>
         <xsd:element name="FirstName" type="NameString" maxOccurs="1"/>
         <xsd:element name="LastName"  type="NameString" maxOccurs="1"/>
     </xsd:sequence>
  </xsd:complexType>
</xsd:schema>

using System.ComponentModel.DataAnnotations;
public class Person
{
     [StringLength(255, ErrorMessage = "Error")]
     public string FirstName { get; set; }
     [StringLength(255, ErrorMessage = "Error")]
     public string LastName { get; set; }
}