UXDataComboBox derives from UXComboBox which means that the control is normally used to perform a single selection. It is a queryable combo box control that utilizes the power of QueryDescriptor to search records in relatively large dataset. Unlike UXComboBox, UXDataComboBox does not have a collection of items bound initially. You need to input the query to UXDataComboBox and handle the query using the QueryDescriptor.

The following code shows how to use UXDataComboBox to query and select a record.

View

<Intersoft:UXDataComboBox x:Name="SampleControl1" DisplayMemberPath="FirstName" Width="150"
                          SelectedValue="{Binding LeaveRequest.EmployeeID, Mode=TwoWay}" SelectedValuePath="EmployeeID"
                          SearchResult="{Binding Employees}"
                          FilterDescriptors="{Binding LookUpDescriptor.FilterDescriptors, Mode=TwoWay}"
                          BusyMode="Always" AutoShowResultBox="True" IsTextSearchEnabled="True"
                          ToolTipService.ToolTip="Try to type in 'a', 'r', or 's' character..."/>

ViewModel

using System;
using System.Collections;
using Intersoft.Client.Data.ComponentModel;
using Intersoft.Client.Framework.Input;
using Intersoft.ClientUI.Samples.DataControls.ModelServices;

namespace Intersoft.ClientUI.Samples.DataControls.ViewModels
{
    public class DataComboBoxViewModel : ViewModelBase
    {
        #region Constructors

        public DataComboBoxViewModel()
        {
            if (!this.IsInDesignMode)
            {
                this.EmployeesSource = EmployeesRepository.Instance;
                this.Presenter = new MessagePresenter();
                this.LookUpDescriptor = new QueryDescriptor();
            }
        }

        #endregion

        #region Fields

        private IEnumerable _employees;
        private QueryDescriptor _lookUpDescriptor;

        #endregion

        #region Properties

        public IEnumerable Employees
        {
            get { return this._employees; }
            set
            {
                if (_employees != value)
                {
                    _employees = value;
                    OnPropertyChanged("Employees");
                }
            }
        }

        protected IDataRepository EmployeesSource { get; set; }

        protected bool IsInDesignMode
        {
            get
            {
                return Intersoft.Client.Framework.ISControl.IsInDesignModeStatic;
            }
        }

        public QueryDescriptor LookUpDescriptor
        {
            get
            {
                return _lookUpDescriptor;
            }
            set
            {
                if (_lookUpDescriptor != value)
                {
                    if (_lookUpDescriptor != null)
                        _lookUpDescriptor.QueryChanged -= new EventHandler(OnLookUpQueryChanged);

                    _lookUpDescriptor = value;
                    _lookUpDescriptor.QueryChanged += new EventHandler(OnLookUpQueryChanged);

                    OnPropertyChanged("LookUpDescriptor");
                }
            }
        }

        protected virtual MessagePresenter Presenter { get; private set; }

        #endregion

        #region Methods

        private void OnLookUpQueryChanged(object sender, EventArgs e)
        {
            this.EmployeesSource.GetData
            (
                this.LookUpDescriptor,
                (employees) =>
                {
                    this.Employees = employees;
                },
                (totalItemCount) =>
                {
                },
                (error) =>
                {
                    this.Presenter.ShowErrorMessage(
                        "An exception has occurred during data loading\n." +
                        "Message: " + error.Message +
                        "Stack Trace: " + error.StackTrace);
                }
            );
        }

        #endregion
    }
}

Notice that you only need to bind the FilterDescriptors in your XAML and handle the QueryChanged in your ViewModel. The UXDataComboBox will pass the filter descriptors based on FilterMemberPath, FilterOperator and user’s input query.

Hope this helps.