Create a store from Code Behind and filter its content and bind it to Combobox Ext.Net 2.2 - filter

Question

I am creating combobox in a component Column in a GridPanel from codebehind. There is requirement to create a store and filter its content according to some condition and bind it to the created combobox. Store is getting bind to combo but filter is not working. Please help me to get the proper solution for this. My code snippet is given below.
List<object> storeDataProductClass= new List<object>();
storeDataProductClass.Add(new { text = "Class0", value = "Class0", productIndex = 0});
storeDataProductClass.Add(new { text = "Class1", value = "Class1", productIndex = 1});
storeDataProductClass.Add(new { text = "Class2", value = "Class2", productIndex = 2});
storeDataProductClass.Add(new { text = "Class3", value = "Class3", productIndex = 3});
storeDataProductClass.Add(new { text = "Class4", value = "Class4", productIndex = 4});
Ext.Net.ComboBox cmbClass = new ComboBox();
cmbClass.ID = "cmbClass_" + i;
Model classModel = new Model();
classModel.Fields.Add(new ModelField("text", ModelFieldType.String));
classModel.Fields.Add(new ModelField("value", ModelFieldType.String));
classModel.Fields.Add(new ModelField("productIndex", ModelFieldType.Int));
Ext.Net.Store storeClass = new Ext.Net.Store();
storeClass.ID = "storeClass_" + i;
storeClass.AutoDataBind = true;
storeClass.Model.Add(classModel);
storeClass.DataSource = storeDataProductClass;
storeClass.DataBind();
storeClass.Filter("productIndex", i.ToString());
cmbClass.Store.Add(storeClass);
cmbClass.DisplayField = "text";
cmbClass.ValueField = "value";
compColumn.Component.Add(cmbClass);