var sParams = "(p.start,p.limit";
var filt = [];
var filterItems = '';

if(p.filters) {
if(p.filters.getCount()>0) {
filt = p.getFilterData();
if(filt.length>0) {
var filters = {};
filters.gridFilters = [];
for(var i=0;i<filt.length;i++){
filters.gridFilters.push(filt[i])
}
filterItems = Ext.encode(filters);
}
}
}

Ext.data.PageMethodProxy.TRANS_ID = 1000;
Ext.data.PageMethodProxy.arr_trans = Array();

Ext.extend(Ext.data.PageMethodProxy, Ext.data.DataProxy, {
load : function(params, reader, callback, scope, arg) {
if(this.fireEvent("beforeload", this, params) !== false){

var p = Ext.apply(params, this.extraParams);
var transId = ++Ext.data.PageMethodProxy.TRANS_ID;
var sParams = "(p.start,p.limit";
var filt = [];
var filterItems = '';

if(p.filters) {
if(p.filters.getCount()>0) {
filt = p.getFilterData();
if(filt.length>0) {
for(var i=0;i<filt.length;i++){
if(filterItems.length==0){
filterItems += '{"gridFilters":[' + Ext.encode(filt[i]);
}else{
filterItems += ', ' + Ext.encode(filt[i]);
}
}
filterItems += ']}';
}
}
}

sParams += ",filterItems,this.handleResponse)";....

// PageMethod
[System.Web.Services.WebMethod(EnableSession = true)]
public static HowToList GetHowTos(int PageNumber, int MaximumRows, string JSON)
{

HowToList howToList = new HowToList();
HowToItem item = null;
JSONGridFilters filter = new JSONGridFilters(JSON);
string selekt = filter.GetFilter();

DataTable dt = howToList.DataSource(selekt);........

// then my deserializer class looks like this

using System.Collections.Generic;
using System.Web.Script.Serialization;

// Example JSON{"gridFilters":[{"field":"title","data":{"type":"string","value":"3d"}}]}

public class JSONGridFilters
{
private GridFilters _filters;

public JSONGridFilters(string JSON)
{
if (!string.IsNullOrEmpty(JSON)) {
JavaScriptSerializer jss = new JavaScriptSerializer();
object test = jss.DeserializeObject(JSON);

if ((test) is Dictionary) {
Dictionary dict = (Dictionary)test;
if (dict.Count > 0) {
if (dict.ContainsKey("gridFilters")) {
_filters = (GridFilters)jss.Deserialize(JSON);
}
}
}
}
}

public string GetFilter()
{
StringBuilder sb = new StringBuilder();

if ((_filters != null)) {
foreach (GridFilter f in _filters.gridFilters) {
if ((f.field != null) && (f.data != null)) {
if (sb.Length == 0) {
sb.Append(f.field).Append(" LIKE '%").Append(f.data.value).Append("%'");
}
else {
sb.Append(" AND ").Append(f.field).Append(" LIKE '%").Append(f.data.value).Append("%'");
}
}
}
}

return sb.ToString();

}
}

internal class GridFilters
{
public List gridFilters;
}

internal class GridFilter
{
public string field;
public FilterPair data;
}

internal class FilterPair
{
public string type;
public object value;
}