wcf collection datameber value is different (client between server)

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C#

WCF

collections

DataContract

PDA client source : made by other person

[System.CodeDom.Compiler.GeneratedCodeAttribute("NetCFSvcUtil", "3.5.0.0")]
[System.SerializableAttribute()]
[System.Diagnostics.DebuggerStepThroughAttribute()]
[System.ComponentModel.DesignerCategoryAttribute("code")]
[System.Xml.Serialization.XmlTypeAttribute(Namespace = "http://tempuri.org/")]
public partial class PersonalShopperDTO
{

    private string staffNumberField;

    private string[] tokensField;

    /// <remarks />
    [System.Xml.Serialization.XmlElementAttribute(Order = 0)]
    public string StaffNumber
    {
        get
        {
            return this.staffNumberField;
        }
        set
        {
            this.staffNumberField = value;
        }
    }

    /// <remarks />
    [System.Xml.Serialization.XmlArrayAttribute(Order = 1)]
    public string[] Tokens
    {
        get
        {
            return this.tokensField;
        }
        set
        {
            this.tokensField = value;
        }
    }
}

WCF soucre : made by me

[DataContract(Namespace = "http://tempuri.org/")]
    [KnownType(typeof(string[]))]
    public class PersonalShopperDTO
    {
        [DataMember]
        public string StaffNumber { get; set; }

        [DataMember]
        public string[] Tokens { get; set; }
    }

-------------------------------------------------------
client value setting : StaffNumber = "1234", Tokens = new string[] { "abc", "edf" }

wcf value => StaffNumber = "1234", Tokens = string[0]

why different Tokens value?

how about wcf DataMember setting??

help me~~