ClientStore.js

Ext.define('MyApp.store.ClientStore', {
    extend: 'Ext.data.Store',    
    config: {
        model: 'MyApp.model.Client',
        storeId: 'clientStore',        
        sorters: [
            { property: 'ClientName', direcion: 'ASC' }
        ],
        
        listeners: {
            beforeload: function(store){

                store.setProxy({
                    type: 'ajax',
                    url: 'http://www.myapp.local/services/GetClients',
                    headers: {
                        'Content-Type': 'application/json'
                    },
                    extraParams: {
                        filterString: Ext.ComponentQuery.query('searchformfield')[0].getValue()
                    },            
                    actionMethods: {
                        read: "POST"
                    },
                    reader: {
                        type: 'json',
                        rootProperty: 'GetClientsResult'
                    },
                    writer: {
                        type: 'json',
                        encodeRequest: true
                    }                       
                });
            }        
       } 
    } 
});