[OperationContract]
Customer[] FindCustomers(string id, string name, string location, ...);

#region

using System;
using System.Data;
using System.Data.SqlClient;
using System.Xml.Serialization;

#endregion

[Serializable]
public class SQLParamSerializationWrapper
{
    #region Constants and Fields

    private SqlParameter param;

    #endregion

    #region Constructors and Destructors

    public SQLParamSerializationWrapper()
    {
        //paramless constructor for serialization
        this.param = new SqlParameter();
    }

    public SQLParamSerializationWrapper(SqlParameter param)
    {
        this.SQLParam = param;
    }

    #endregion

    #region Properties

    public DbType DbType
    {
        get
        {
            return this.SQLParam.DbType;
        }
        set
        {
            this.SQLParam.DbType = value;
        }
    }

    public ParameterDirection Direction
    {
        get
        {
            return this.SQLParam.Direction;
        }
        set
        {
            this.SQLParam.Direction = value;
        }
    }

    public string ParameterName
    {
        get
        {
            return this.SQLParam.ParameterName;
        }
        set
        {
            this.SQLParam.ParameterName = value;
        }
    }

    [XmlIgnore]
    public SqlParameter SQLParam
    {
        get
        {
            return this.param;
        }
        set
        {
            this.param = value;
        }
    }

    public int Size
    {
        get
        {
            return this.SQLParam.Size;
        }
        set
        {
            this.SQLParam.Size = value;
        }
    }

    public object Value
    {
        get
        {
            return this.SQLParam.Value;
        }
        set
        {
            this.SQLParam.Value = value;
        }
    }

    #endregion
}

List<SQLParamSerializationWrapper> procParams = new List<SQLParamSerializationWrapper>();
            SqlParameter startdate = new SqlParameter("dateStart", new DateTime(2011, 9, 5));
            SqlParameter enddate = new SqlParameter("dateEnd", new DateTime(2011, 9, 6));

            SQLParamSerializationWrapper startDateWrapper = new SQLParamSerializationWrapper(startdate);
            SQLParamSerializationWrapper endDateWrapper = new SQLParamSerializationWrapper(enddate);

            procParams.Add(startDateWrapper);
            procParams.Add(endDateWrapper);

            string paramsAsXML = "";

            using (var sw = new StringWriter())
            {
                using (var xw = XmlWriter.Create(sw))
                {
                    XmlSerializer xs = new XmlSerializer(procParams.GetType());
                    xs.Serialize(xw, procParams);
                }
                paramsAsXML = sw.ToString();
            }

var procParams = new List<SqlParameter>();

StringReader sr = new StringReader(parm.Value);
                        // Create an instance of the XmlSerializer specifying type.
                        XmlSerializer deserializer = new XmlSerializer(typeof(List<SQLParamSerializationWrapper>));

                        List<SQLParamSerializationWrapper> sqlParamWrapper = (List<SQLParamSerializationWrapper>)deserializer.Deserialize(sr);

                        foreach (var param in sqlParamWrapper)
                        {
                            procParams.Add(param.SQLParam);
                        }