combo box in Extjs does not send right value

I'm very confused, please help me to get rid of this problem. I have two fields 1. display 2. value:

    new Ext.form.ComboBox({
      width: 200,
      height:'50',
      id:'Keyword',
      triggerAction: 'all', 
                     mode: 'local',
      store: natureStore ,  
      hiddenNam开发者_运维问答e:'value',
      valueField: 'value',  
      anyMatch: true,
                     displayField: 'display',   
      emptyText:window.parent.localisedConstants.menusearch,
      listeners: {
     'render': function(c) {
      c.el.on('keypress', filterTree, c, {buffer: 350});
      }
     }
    })

c.target.value always return display field instead of value field.

An example here would definitely help, but I imagine the problem involves the method in which you are retrieving the value of the combobox. The combobox getValue function:

http://dev.sencha.com/deploy/dev/docs/source/Combo.html#method-Ext.form.ComboBox-getValue

should correctly pull the 'value field' value.