How To:auto select the first item in radcombobox when use collectionViewSource?

[lee hom]

Hi!
   I want auto select first item in radcombobox,like microsoft's combobox,how can i do?
   this is the code and project:

<UserControl x:Class="Silverlight.Rad"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    mc:Ignorable="d"
    d:DesignHeight="300" d:DesignWidth="400"
             xmlns:my="clr-namespace:Silverlight"
             xmlns:telerik="http://schemas.telerik.com/2008/xaml/presentation">
    <UserControl.Resources>
        <my:Data x:Key="data" />
        <CollectionViewSource x:Key="dataSchoolsViewSource" Source="{Binding Path=Schools, Source={StaticResource data}}" />
        <CollectionViewSource x:Key="dataSchoolsCollegesViewSource" Source="{Binding Path=Colleges, Source={StaticResource dataSchoolsViewSource}}" />
        <CollectionViewSource x:Key="dataSchoolsCollegesDepartmentsViewSource" Source="{Binding Path=Departments, Source={StaticResource dataSchoolsCollegesViewSource}}" />
    </UserControl.Resources>
    <Grid x:Name="LayoutRoot" Background="White">
        <StackPanel>
            <my:MyRadComboBox DisplayMemberPath="Name" ItemsSource="{Binding Source={StaticResource dataSchoolsViewSource}}" />
            <my:MyRadComboBox DisplayMemberPath="Name" ItemsSource="{Binding Source={StaticResource dataSchoolsCollegesViewSource}}" />
            <my:MyRadComboBox DisplayMemberPath="Name" ItemsSource="{Binding Source={StaticResource dataSchoolsCollegesDepartmentsViewSource}}" />
        </StackPanel>

    </Grid>
</UserControl>

using Telerik.Windows.Controls;
using System.ComponentModel;

namespace Silverlight
{
    public class MyRadComboBox : RadComboBox
    {
        /// <summary>
        /// Invoked when the <see cref="P:System.Windows.Controls.ItemsControl.Items"/> property changes.
        /// </summary>
        /// <param name="e">Information about the change.</param>
        protected override void OnItemsChanged(System.Collections.Specialized.NotifyCollectionChangedEventArgs e)
        {
            base.OnItemsChanged(e);
            if (this.ItemsSource != null
                && e.Action == System.Collections.Specialized.NotifyCollectionChangedAction.Reset
                && this.ItemsSource is ICollectionView)
            {

                (this.ItemsSource as ICollectionView).CurrentChanged += CollectionView_CurrentChanged;
            }
        }

        /// <summary>
        /// Handles the CurrentChanged event of the CollectionView control.
        /// </summary>
        /// <param name="sender">The source of the event.</param>
        /// <param name="e">The <see cref="System.EventArgs"/> instance containing the event data.</param>
        void CollectionView_CurrentChanged(object sender, EventArgs e)
        {
            var collectionView = this.ItemsSource as ICollectionView;
            if (collectionView != null && this.SelectedItem != collectionView.CurrentItem)
                this.SelectedItem = collectionView.CurrentItem;
        }

        /// <summary>
        /// Called when the selection changes.
        /// </summary>
        /// <param name="e">The event data.</param>
        protected override void OnSelectionChanged(System.Windows.Controls.SelectionChangedEventArgs e)
        {
            base.OnSelectionChanged(e);
            if (this.SelectedItem == null || !(this.ItemsSource is ICollectionView)) return;
            var collectionView = this.ItemsSource as ICollectionView;
            if (collectionView.CurrentItem != this.SelectedItem)
                collectionView.MoveCurrentTo(this.SelectedItem);
        }
    }
}

namespace Silverlight
{

    public class Department
    {
        public College College { get; set; }

        public string Name
        {
            get;
            set;
        }
    }

    public class College
    {
        public School School { get; set; }

        ObservableCollection<Department> departments = new ObservableCollection<Department>();

        public ObservableCollection<Department> Departments
        {
            get { return departments; }
        }

        public string Name
        {
            get;
            set;
        }
    }

    public class School
    {
        ObservableCollection<College> colleges = new ObservableCollection<College>();

        public ObservableCollection<College> Colleges
        {
            get { return colleges; }
        }

        public string Name
        {
            get;
            set;
        }
    }

    public class Data
    {
        ObservableCollection<School> schools = new ObservableCollection<School>();

        public ObservableCollection<School> Schools
        {
            get { return schools; }
        }

        ObservableCollection<Department> departments = new ObservableCollection<Department>();

        public ObservableCollection<Department> Departments
        {
            get { return departments; }
        }

        public Data()
        {
            School school = new School() { Name = "S1" };

            College college = new College() { Name = "S1_Col1", School = school };
            college.Departments.Add(new Department() { Name = "S1_Col1_Dpt1", College = college });
            college.Departments.Add(new Department() { Name = "S1_Col1_Dpt2", College = college });
            college.Departments.Add(new Department() { Name = "S1_Col1_Dpt3", College = college });
            college.Departments.Add(new Department() { Name = "S1_Col1_Dpt4", College = college });

            foreach (Department dpt in college.Departments)
            {
                departments.Add(dpt);
            }

            school.Colleges.Add(college);

            college = new College() { Name = "S1_Col2", School = school };
            college.Departments.Add(new Department() { Name = "S1_Col2_Dpt1", College = college });
            college.Departments.Add(new Department() { Name = "S1_Col2_Dpt2", College = college });
            college.Departments.Add(new Department() { Name = "S1_Col2_Dpt3", College = college });
            college.Departments.Add(new Department() { Name = "S1_Col2_Dpt4", College = college });
            school.Colleges.Add(college);

            foreach (Department dpt in college.Departments)
            {
                departments.Add(dpt);
            }

            Schools.Add(school);

            school = new School() { Name = "S2" };

            college = new College() { Name = "S2_Col1", School = school };
            college.Departments.Add(new Department() { Name = "S2_Col1_Dpt1", College = college });
            college.Departments.Add(new Department() { Name = "S2_Col1_Dpt2", College = college });
            college.Departments.Add(new Department() { Name = "S2_Col1_Dpt3", College = college });
            college.Departments.Add(new Department() { Name = "S2_Col1_Dpt4", College = college });
            school.Colleges.Add(college);
            foreach (Department dpt in college.Departments)
            {
                departments.Add(dpt);
            }


            college = new College() { Name = "S2_Col2", School = school };
            college.Departments.Add(new Department() { Name = "S2_Col2_Dpt1", College = college });
            college.Departments.Add(new Department() { Name = "S2_Col2_Dpt2", College = college });
            college.Departments.Add(new Department() { Name = "S2_Col2_Dpt3", College = college });
            college.Departments.Add(new Department() { Name = "S2_Col2_Dpt4", College = college });
            school.Colleges.Add(college);
            foreach (Department dpt in college.Departments)
            {
                departments.Add(dpt);
            }


            Schools.Add(school);
        }
    }
}

PROJECT Download

[Konstantina]

Hi lee hom,

Thank you for the code snippets and for the provided project.

To select the first item in RadComboBox you can use the SelectedIndex property or the SelectedItem property of the ComboBox. You can find more information about them in this help article: http://www.telerik.com/help/silverlight/radcombobox-features-selection.html

Hope this helps. If you need further assistance please let us know.

Sincerely yours,
Konstantina
the Telerik team

[lee hom]

OH  I SEE, override the itemschaned funtion.
thank you