[Solved] ComboBox and SelectedIndex

[Peter Bogoyavlensky]

Please, can you help me with this question:

I have a grid with combobox column. All of these comboboxes have different DataSorce property (assigned thouth intercepting CellEditorInitialized event):

Private Sub gridSort_CellEditorInitialized(ByVal sender As Object, ByVal e As Telerik.WinControls.UI.GridViewCellEventArgs) Handles gridSort.CellEditorInitialized

Dim i As Integer

If gridSort.CurrentColumn.HeaderText = "Order" Then

Dim editor As Telerik.WinControls.UI.RadComboBoxEditor = gridSort.ActiveEditor

Dim editorElement As Telerik.WinControls.UI.RadComboBoxEditorElement = editor.EditorElement

If gridSort.Rows.IndexOf(gridSort.CurrentRow) = 1 Then

i = editorElement.SelectedIndex

editorElement.DataSource = New String() {"Minimized", "Maximized"}

editorElement.SelectedIndex = i

If i < 0 Then

Dim ii As Integer = 0

For Each ss As String In editorElement.DataSource

If ss = gridSort.CurrentRow.Cells.Item(1).Value Then

editorElement.SelectedIndex = ii

Exit For

End If

ii += 1

Next

End If

Else

i = editorElement.SelectedIndex

editorElement.DataSource = New String() {"Ascending", "Descending"}

editorElement.SelectedIndex = i

End If

End If

End Sub

1. Every time editorElement.SelectedIndex have value -1 (and I must set value by searching throuh DataSource list and comparing with cell Value). For values Minimized/Maximized it's done and work fine, but for values Ascending/Descending it's not and when I click on combobox field - it's filled by empty sring.

Comparing with Value of cell is not fine because here can be some duplicated values (sic!) and I can not determine what value was in this cell before. Is here some method of determine SelectedIndex after changing of value?

2. I want to collect data choosen by user. But ComboBox cell in grid have not SelectedIndex (or I can not find it?) and I must to obtain it from Value property. Problem is similiar with previous question - how can I find a real position of value in DataSource list?

[Victor]

Hi Peter Bogoyavlensky,

Here is sample code to demonstrate the required functionality:

Imports Telerik.WinControls.UI

Public Class Form1
    Dim list As List(Of String) = New List(Of String)

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        list.Add("Value1")
        list.Add("Value2")
        list.Add("Value3")
        list.Add("Value4")
        Dim column As GridViewComboBoxColumn = New GridViewComboBoxColumn
        column.DataSource = list
        Me.RadGridView1.Columns.Add(column)
    End Sub

    Private Sub RadGridView1_CellBeginEdit(ByVal sender As System.Object, ByVal e As Telerik.WinControls.UI.GridViewCellCancelEventArgs) Handles RadGridView1.CellBeginEdit
        Dim editor As IInputEditor = Me.RadGridView1.ActiveEditor
        If TypeOf (editor) Is RadComboBoxEditor Then
            Dim comboElement As RadComboBoxElement = CType(CType(editor, RadComboBoxEditor).EditorElement, RadComboBoxElement)
            AddHandler (comboElement.SelectedIndexChanged), AddressOf SelectedIndexChanged
        End If
    End Sub

    Private Sub RadGridView1_CellEndEdit(ByVal sender As System.Object, ByVal e As Telerik.WinControls.UI.GridViewCellEventArgs) Handles RadGridView1.CellEndEdit
        Dim editor As IInputEditor = Me.RadGridView1.ActiveEditor
        If TypeOf (editor) Is RadComboBoxEditor Then
            Dim comboElement As RadComboBoxElement = CType(CType(editor, RadComboBoxEditor).EditorElement, RadComboBoxElement)
            RemoveHandler (comboElement.SelectedIndexChanged), AddressOf SelectedIndexChanged
        End If
    End Sub

    Private Sub SelectedIndexChanged(ByVal sender As System.Object, ByVal e As EventArgs)
        Dim index As Integer = CType(sender, RadComboBoxElement).SelectedIndex
        If index > -1 Then
            MessageBox.Show("Selected Index changed. Value: " + list(index))
        End If
    End Sub
End Class

I hope I have addressed the issue correctly. Please write again if you need further assistance.

All the best,
Victor
the Telerik team

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[Rick Petersen]

This solution is perfect.  Using your solution, Victor, I was able to overcome the general issue of not having access to an SelectedIndexChanged method within a GridViewComboBoxColumn.  Not that it is more than trivial to do the conversion, but below is the C# implementation of your suggestions:

        private void radGridView2_CellBeginEdit(object sender, GridViewCellCancelEventArgs e)
        {
            IInputEditor editor = this.radGridView2.ActiveEditor;
            if (editor.GetType() == typeof(RadComboBoxEditor))
            {
                RadComboBoxElement comboElement = (RadComboBoxElement)((RadComboBoxEditor)editor).EditorElement;
                comboElement.SelectedIndexChanged += new EventHandler(comboElement_SelectedIndexChanged);
            }
        }

        private void radGridView2_CellEndEdit(object sender, GridViewCellEventArgs e)
        {
            IInputEditor editor = this.radGridView2.ActiveEditor;
            if (editor.GetType() == typeof(RadComboBoxEditor))
            {
                RadComboBoxElement comboElement = (RadComboBoxElement)((RadComboBoxEditor)editor).EditorElement;
                comboElement.SelectedIndexChanged -= new EventHandler(comboElement_SelectedIndexChanged);
            }
        }

        void comboElement_SelectedIndexChanged(object sender, EventArgs e)
        {
            int index = (int)(((RadComboBoxElement)sender).SelectedIndex);
            MessageBox.Show("Selected Index Changed. Value: " + index);
        }

Well, I didn't bother using the index to lookup a value in a list, but that's even more trivial to finish out.

Anyway, doing this has given me a hook into the indexchanged event which will allow me to apply the logic I needed.  I'm so pleased, thank you for the contribution.

[Victor]

Hello Rick,

Thank you very much for the feedback and for the C# example. We are ready to offer further assistance if you need it.

 
Kind regards,
Victor
the Telerik team

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[Saurabh Garg]

Hi Victor,

I am trying to implement a logic similar to above. The code is running fine for the first time, but when you select other row, the selected index property first shows previous selected index and then current index. Please help me.

Thanks in advance.
Regards,
Saurabh Garg

[Victor]

Hi Saurabh Garg,

Thank you for writing. Please explain in more details what the issue is since I cannot reproduce the behavior you described. Some sample code would be most illustrative. I am looking forward to your reply.

Regards,
Victor
the Telerik team

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[Saurabh Garg]

Victor here is my code. Please try to edit more than one row to show it's behaviour, i hope that will generate the required behaviour.

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using Telerik.WinControls.UI;

namespace TelerikGridEditing
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            bindGrid();
            GridLayout();
        }

        private void bindGrid()
        {
            DataTable dt = new DataTable();
            dt.Columns.Add("ProductId");
            dt.Columns.Add("ProductName");
            dt.Columns.Add("ProductDesciption");
            dt.Rows.Add(1, "IPod Classic 80GB", "Description of product");
            dt.Rows.Add(2, "IPod Touch 32GB", "Description of product");
            dt.Rows.Add(3, "DishWasher", "Description of product");
            dt.Rows.Add(4, "Microwave Oven", "Description of product");
            dt.Rows.Add(5, "WashingMachine", "Description of product");
            dt.Rows.Add(6, "Coffee Mug", "Description of product");
            dt.Rows.Add(7, "Umbrella", "Description of product");

            GridViewTextBoxColumn col1 = new GridViewTextBoxColumn();
            col1.FieldName = "ProductId";

            GridViewTextBoxColumn col2 = new GridViewTextBoxColumn();
            col1.FieldName = "ProductName";

            GridViewTextBoxColumn col3 = new GridViewTextBoxColumn();
            col1.FieldName = "ProductDesciption";

            GridViewComboBoxColumn col4 = new GridViewComboBoxColumn();

            DataTable dtQty = new DataTable();
            dtQty.Columns.Add("dataValue");
            dtQty.Columns.Add("displayValue");
            for (int i = 0; i <= 10; i++)
                dtQty.Rows.Add(i, i);
            col4.DataSource = dtQty;
            col4.ValueMember = "dataValue";
            col4.DisplayMember = "displayValue";
            col4.FieldName = "dataValue";



            radGridView1.MasterGridViewTemplate.Columns.Add(col1);
            radGridView1.MasterGridViewTemplate.Columns.Add(col2);
            radGridView1.MasterGridViewTemplate.Columns.Add(col3);
            radGridView1.MasterGridViewTemplate.Columns.Add(col4);


            foreach (DataRow dr in dt.Rows)
                radGridView1.MasterGridViewTemplate.Rows.Add(dr["ProductId"], dr["ProductName"], dr["ProductDesciption"], "0");
        }




        private void GridLayout()
        {
            radGridView1.Columns[0].Width = 50;
            radGridView1.Columns[1].Width = 100;
            radGridView1.Columns[2].Width = 200;
            radGridView1.Columns[3].Width = 50;

            radGridView1.Width = 700;

            radGridView1.MasterGridViewTemplate.Columns[0].HeaderText = "Id";
            radGridView1.MasterGridViewTemplate.Columns[0].ReadOnly = true;
            radGridView1.MasterGridViewTemplate.Columns[1].HeaderText = "Name";
            radGridView1.MasterGridViewTemplate.Columns[1].ReadOnly = true;
            radGridView1.MasterGridViewTemplate.Columns[2].HeaderText = "Description";
            radGridView1.MasterGridViewTemplate.Columns[2].ReadOnly = true;
            radGridView1.MasterGridViewTemplate.Columns[3].HeaderText = "Order";

            radGridView1.MasterGridViewTemplate.AllowAddNewRow = false;
            radGridView1.MasterGridViewTemplate.EnableGrouping = false;
        }

        private void radGridView1_CellBeginEdit(object sender, GridViewCellCancelEventArgs e)
        {
            MessageBox.Show("Start");
            IInputEditor editor = radGridView1.ActiveEditor;

            if (editor.GetType() == typeof(RadComboBoxEditor))
            {
                RadComboBoxElement comboElement = (RadComboBoxElement) ((RadComboBoxEditor)editor).EditorElement;
                comboElement.SelectedIndexChanged += new EventHandler(comboElement_SelectedIndexChanged);

            }
        }

        void comboElement_SelectedIndexChanged(object sender, EventArgs e)
        {
            int index = Convert.ToInt32(((RadComboBoxElement)sender).SelectedValue);
            MessageBox.Show("Selected Index Changed. Value: " + index);

        }

        private void radGridView1_CellEndEdit(object sender, GridViewCellEventArgs e)
        {
            MessageBox.Show("Edit End");
            IInputEditor editor = radGridView1.ActiveEditor;
            if (editor.GetType() == typeof(RadComboBoxEditor))
            {
                RadComboBoxElement comboElement = (RadComboBoxElement)((RadComboBoxEditor)editor).EditorElement;
                comboElement.SelectedIndexChanged -= new EventHandler(comboElement_SelectedIndexChanged);

            }
        }

    }
}

[Victor]

Hello Saurabh Garg,

Thank you for the code it demonstrated the issue nicely. This is not a bug but merely a side effect which originates from the synchronization of RadListBoxElement inside RadComboBoxElement with the CurrencyManager object which keeps track of the selected position in the data source. In order to not get the previous index you need to assign a new BindingContext in the SelectedIndexChanged event. For example your SelectedIndexChanged event handler can be re-written:

 

void comboElement_SelectedIndexChanged(object sender, EventArgs e)
{
    RadComboBoxElement combo = (RadComboBoxElement)sender;
    int index = combo.SelectedIndex;
    if (index == -1)
    {
        combo.ListBoxElement.BindingContext = new BindingContext();
    }
}

Write again if you have other questions.

 

All the best,
Victor
the Telerik team

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[Saurabh Garg]

Thanks a lot Victor. It really worked.