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SelectedValueChangedEvent

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MultiColumn ComboBox
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Claude
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Claude asked on 10 Dec 2020, 01:32 AM

I have the following code in the event

 private void mccbSelectTheme_SelectedValueChanged(object sender, EventArgs e)
        {
            string cc = mccbSelectTheme.EditorControl.CurrentRow.Cells[1].Value.ToString();

         }

 

I keep getting a System.Null reference exception when I click the dropdown arrow.  

 

The control is loaded with2 columns with column 1 not visible.  

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Nadya
Telerik team
answered on 10 Dec 2020, 09:51 AM

Hello, Claude,

Following the provided information I created a MultiColumnComboBox with two columns, first of them is not visible. However, I am not receiving an error when clicking on the dropdown arrow. You can see the result on my end in the attached gif file. Below is my sample project:

 public RadForm1()
 {
     InitializeComponent();
     DataTable table = new DataTable();
     table.Columns.Add("ID", typeof(int));
     table.Columns.Add("Employee", typeof(string));
     
     table.Rows.Add(25, "David");
     table.Rows.Add(50,  "Sam");
     table.Rows.Add(10, "Christoff");
     table.Rows.Add(21, "Janet");
     table.Rows.Add(100, "Melanie");

     this.radMultiColumnComboBox1.DataSource = table;
     this.radMultiColumnComboBox1.Columns[0].IsVisible = false;
     this.radMultiColumnComboBox1.EditorControl.AutoSizeColumnsMode = GridViewAutoSizeColumnsMode.Fill;
     this.radMultiColumnComboBox1.SelectedValueChanged += this.RadMultiColumnComboBox1_SelectedValueChanged;
 }

 private void RadMultiColumnComboBox1_SelectedValueChanged(object sender, EventArgs e)
 {
     string cc = radMultiColumnComboBox1.EditorControl.CurrentRow.Cells[1].Value.ToString();
 }

Could you give it a try and let me know how it differs from your set up. Am I missing something?

I am looking forward to your reply.

Regards,
Nadya
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Claude
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answered on 10 Dec 2020, 05:41 PM

Here is my code.  Also attached error message when I click on the dropdown

private void frmSettings_Load(object sender, EventArgs e)
        {
            ThemeResolutionService.ApplicationThemeName = "Desert";
            //disable event
            

            this.mccbSelectTheme.SelectedValueChanged -= this.mccbSelectTheme_SelectedValueChanged;

            this.mccbSelectTheme.MultiColumnComboBoxElement.Columns.Add("Name");
            this.mccbSelectTheme.MultiColumnComboBoxElement.Columns.Add("Id");
            mccbSelectTheme.Columns[1].IsVisible = false;


            this.mccbSelectTheme.EditorControl.Rows.Add("Aqua", "Aqua");
            this.mccbSelectTheme.EditorControl.Rows.Add("Breeze", "Breeze");
            this.mccbSelectTheme.EditorControl.Rows.Add("Desert", "Desert");
            this.mccbSelectTheme.EditorControl.Rows.Add("Fluent", "Fluent");
            this.mccbSelectTheme.EditorControl.Rows.Add("Fluent Dark", "FluentDark");
            this.mccbSelectTheme.EditorControl.Rows.Add("Black", "Office2010Black");
            this.mccbSelectTheme.SelectedIndex = 0;
            //enable event
            this.mccbSelectTheme.SelectedValueChanged += this.mccbSelectTheme_SelectedValueChanged;

        }

        private void mccbSelectTheme_SelectedValueChanged(object sender, EventArgs e)
        {
            string cc = mccbSelectTheme.EditorControl.CurrentRow.Cells[1].Value.ToString();

            ThemeResolutionService.ApplicationThemeName = cc;

        }

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Claude
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answered on 10 Dec 2020, 05:59 PM

I changed my code to mimic yours using a DataTable, but have the same results.  I can click the control with no problem.  Only occurs if I click on the dropdown arrow.  AS soon as I click on the arrow it errors out.  Box does not drop down.'

private void frmSettings_Load(object sender, EventArgs e)
        {
            ThemeResolutionService.ApplicationThemeName = "Desert";
            //disable event
            this.mccbSelectTheme.SelectedValueChanged -= this.mccbSelectTheme_SelectedValueChanged;

            DataTable dtThemes = new DataTable();

            dtThemes.Columns.Add("Name", typeof(string));
            dtThemes.Columns.Add("ThemeName", typeof(string));
            dtThemes.Rows.Add("Aqua", "Aqua");
            dtThemes.Rows.Add("Breeze", "Breeze");
            dtThemes.Rows.Add("Desert", "Desert");
            dtThemes.Rows.Add("Fluent", "Fluent");
            dtThemes.Rows.Add("Fluent Dark", "FluentDark");
            dtThemes.Rows.Add("Black", "Office2010Black");
            this.mccbSelectTheme.DataSource = dtThemes; ;
            this.mccbSelectTheme.Columns[1].IsVisible = false;
            this.mccbSelectTheme.SelectedIndex = 0;
            this.mccbSelectTheme.EditorControl.AutoSizeColumnsMode = GridViewAutoSizeColumnsMode.Fill;
            //enable event
            this.mccbSelectTheme.SelectedValueChanged += this.mccbSelectTheme_SelectedValueChanged;

        }

        private void mccbSelectTheme_SelectedValueChanged(object sender, EventArgs e)
        {

            ThemeResolutionService.ApplicationThemeName = mccbSelectTheme.EditorControl.CurrentRow.Cells[1].Value.ToString(); ;

        }

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Claude
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answered on 10 Dec 2020, 07:30 PM

This is a simple app that shows the problem.  DropBox link attached.

https://www.dropbox.com/t/7v6Jvn0WX342PXDJ

 

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Nadya
Telerik team
answered on 11 Dec 2020, 10:24 AM

Hello, Claude,

The provided modified project is greatly appreciated. I was able to run it locally however I did not reproduce the error on my end when clicking the drop-down arrow. Please refer to the attached gif file that demonstrates the result. From the provided code snippet I see that you use ThemeResolutionService.ApplicationThemeName = "Desert" and change it accordingly in the project. Still, the error does not reproduce. 

Could you share more information about the error that you get, a stack trace would be greatly appreciated? Which Telerik version you use in your project? 

I am looking forward to your reply.

Regards,
Nadya
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Claude
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answered on 11 Dec 2020, 05:56 PM

Thank you for your reply.   I am using the latest version, framework 4.7.2

 

Here is the call stack

 

>TelerikWinFormsApp8.exe!TelerikWinFormsApp8.RadForm1.RadMultiColumnComboBox1_SelectedValueChanged(object sender, System.EventArgs e) Line 44C#
 Telerik.WinControls.GridView.dll!Telerik.WinControls.UI.RadMultiColumnComboBox.OnSelectedValueChanged(System.EventArgs e)Unknown
 Telerik.WinControls.GridView.dll!Telerik.WinControls.UI.RadMultiColumnComboBox.comboBoxElement_SelectedValueChanged(object sender, System.EventArgs e)Unknown
 Telerik.WinControls.UI.dll!Telerik.WinControls.UI.BaseComboBoxElement.OnSelectedValueChanged(System.EventArgs e)Unknown
 Telerik.WinControls.GridView.dll!Telerik.WinControls.UI.RadMultiColumnComboBoxElement.FireSelectionEvents(Telerik.WinControls.UI.CurrentRowChangedEventArgs e)Unknown
 Telerik.WinControls.GridView.dll!Telerik.WinControls.UI.RadMultiColumnComboBoxElement.OnGrid_CurrentRowChanged(object sender, Telerik.WinControls.UI.CurrentRowChangedEventArgs e)Unknown
 Telerik.WinControls.GridView.dll!Telerik.WinControls.UI.RadGridView.OnCurrentRowChanged(object sender, Telerik.WinControls.UI.CurrentRowChangedEventArgs e)Unknown
 Telerik.WinControls.GridView.dll!Telerik.WinControls.UI.EventDispatcher.RaiseEvent<Telerik.WinControls.UI.CurrentRowChangedEventArgs>(object eventKey, object sender, Telerik.WinControls.UI.CurrentRowChangedEventArgs args)Unknown
 Telerik.WinControls.GridView.dll!Telerik.WinControls.UI.MasterGridViewTemplate.ChangeCurrentRow(Telerik.WinControls.UI.GridViewRowInfo oldRow, Telerik.WinControls.UI.GridViewRowInfo row, Telerik.WinControls.UI.GridViewTemplate viewTemplate)Unknown
 Telerik.WinControls.GridView.dll!Telerik.WinControls.UI.MasterGridViewTemplate.SetPositionCore(Telerik.WinControls.UI.GridViewRowInfo newRow, Telerik.WinControls.UI.GridViewColumn newColumn, Telerik.WinControls.UI.GridViewRowInfo oldRow, Telerik.WinControls.UI.GridViewColumn oldColumn, bool validateRowChange)Unknown
 Telerik.WinControls.GridView.dll!Telerik.WinControls.UI.MasterGridViewTemplate.SetPosition(Telerik.WinControls.UI.GridViewRowInfo row, Telerik.WinControls.UI.GridViewColumn column, bool validateRowChange)Unknown
 Telerik.WinControls.GridView.dll!Telerik.WinControls.UI.MasterGridViewTemplate.ProcessCurrentChanged(Telerik.WinControls.UI.GridViewEvent eventData)Unknown
 Telerik.WinControls.GridView.dll!Telerik.WinControls.UI.MasterGridViewTemplate.ProcessEventCore(Telerik.WinControls.UI.GridViewEvent eventData)Unknown
 Telerik.WinControls.GridView.dll!Telerik.WinControls.UI.GridViewTemplate.Telerik.WinControls.UI.IGridViewEventListener.ProcessEvent(Telerik.WinControls.UI.GridViewEvent eventData)Unknown
 Telerik.WinControls.GridView.dll!Telerik.WinControls.UI.GridViewEventProcessEntity.ProcessCollection(Telerik.WinControls.UI.GridViewEvent gridEvent, Telerik.WinControls.UI.PriorityWeakReferenceList list, Telerik.WinControls.UI.GridEventProcessMode processMode)Unknown
 Telerik.WinControls.GridView.dll!Telerik.WinControls.UI.GridViewSynchronizationService.NotifyListeners(Telerik.WinControls.UI.GridViewEvent gridEvent)Unknown
 Telerik.WinControls.GridView.dll!Telerik.WinControls.UI.GridViewSynchronizationService.FlushEvents()Unknown
 Telerik.WinControls.GridView.dll!Telerik.WinControls.UI.GridViewSynchronizationService.DispatchEvent(Telerik.WinControls.UI.GridViewEvent gridEvent)Unknown
 Telerik.WinControls.GridView.dll!Telerik.WinControls.UI.GridViewSynchronizationService.RaiseCurrentChanged(Telerik.WinControls.UI.GridViewTemplate template, Telerik.WinControls.UI.GridViewRowInfo row, Telerik.WinControls.UI.GridViewColumn column, bool user)Unknown
 Telerik.WinControls.GridView.dll!Telerik.WinControls.UI.MasterGridViewTemplate.CurrentRow.set(Telerik.WinControls.UI.GridViewRowInfo value)Unknown
 Telerik.WinControls.GridView.dll!Telerik.WinControls.UI.RadGridView.CurrentRow.set(Telerik.WinControls.UI.GridViewRowInfo value)Unknown
 Telerik.WinControls.GridView.dll!Telerik.WinControls.UI.MultiColumnComboPopupForm.Rows_CollectionChanged(object sender, Telerik.WinControls.Data.NotifyCollectionChangedEventArgs e)Unknown
 Telerik.WinControls.GridView.dll!Telerik.WinControls.UI.GridViewRowCollection.OnCollectionChanged(Telerik.WinControls.Data.NotifyCollectionChangedEventArgs args)Unknown
 Telerik.WinControls.GridView.dll!Telerik.WinControls.UI.GridViewRowCollection.ListSource_CollectionChanged(object sender, Telerik.WinControls.Data.NotifyCollectionChangedEventArgs e)Unknown
 Telerik.WinControls.dll!Telerik.WinControls.Data.RadListSource<System.__Canon>.OnCollectionChanged(Telerik.WinControls.Data.NotifyCollectionChangedEventArgs e)Unknown
 Telerik.WinControls.dll!Telerik.WinControls.Data.RadListSource<System.__Canon>.EndUpdate(bool notifyUpdates)Unknown
 Telerik.WinControls.GridView.dll!Telerik.WinControls.UI.GridViewTemplate.EndUpdate(bool notify, Telerik.WinControls.UI.DataViewChangedEventArgs e)Unknown
 Telerik.WinControls.GridView.dll!Telerik.WinControls.UI.MasterGridViewTemplate.EndUpdate(bool notify, Telerik.WinControls.UI.DataViewChangedEventArgs e)Unknown
 Telerik.WinControls.GridView.dll!Telerik.WinControls.UI.GridViewTemplate.EndUpdate()Unknown
 Telerik.WinControls.GridView.dll!Telerik.WinControls.UI.RadGridViewElement.DpiScaleChanged(System.Drawing.SizeF scaleFactor)Unknown
 Telerik.WinControls.dll!Telerik.WinControls.RadElement.DpiScaleChanged(System.Drawing.SizeF scaleFactor)Unknown
 Telerik.WinControls.dll!Telerik.WinControls.RootRadElement.DpiScaleChanged(System.Drawing.SizeF scaleFactor)Unknown
 Telerik.WinControls.dll!Telerik.WinControls.RadControl.ScaleControl(System.Drawing.SizeF factor, System.Windows.Forms.BoundsSpecified specified)Unknown
 System.Windows.Forms.dll!System.Windows.Forms.Control.ScaleControl(System.Drawing.SizeF includedFactor, System.Drawing.SizeF excludedFactor, System.Windows.Forms.Control requestingControl)Unknown
 System.Windows.Forms.dll!System.Windows.Forms.Control.Scale(System.Drawing.SizeF factor)Unknown
 System.Windows.Forms.dll!System.Windows.Forms.Control.Scale(System.Drawing.SizeF factor)Unknown
 Telerik.WinControls.UI.dll!Telerik.WinControls.UI.RadPopupControlBase.ShowPopupCore(System.Drawing.Size size, System.Drawing.Point location)Unknown
 Telerik.WinControls.UI.dll!Telerik.WinControls.UI.RadPopupControlBase.ShowPopup(System.Drawing.Rectangle alignmentRectangle)Unknown
 Telerik.WinControls.GridView.dll!Telerik.WinControls.UI.MultiColumnComboPopupForm.ShowPopup(System.Drawing.Rectangle alignmentRectangle)Unknown
 Telerik.WinControls.UI.dll!Telerik.WinControls.UI.PopupEditorBaseElement.ShowPopup()Unknown
 Telerik.WinControls.UI.dll!Telerik.WinControls.UI.BaseComboBoxElement.ShowPopup()Unknown
 Telerik.WinControls.UI.dll!Telerik.WinControls.UI.BaseComboBoxElement.OnBubbleEvent(Telerik.WinControls.RadElement sender, Telerik.WinControls.RoutedEventArgs args)Unknown
 Telerik.WinControls.dll!Telerik.WinControls.RadElement.RaiseBubbleEvent(Telerik.WinControls.RadElement sender, Telerik.WinControls.RoutedEventArgs args)Unknown
 Telerik.WinControls.dll!Telerik.WinControls.RadItem.RaiseBubbleEvent(Telerik.WinControls.RadElement sender, Telerik.WinControls.RoutedEventArgs args)Unknown
 Telerik.WinControls.dll!Telerik.WinControls.RadElement.RaiseBubbleEvent(Telerik.WinControls.RadElement sender, Telerik.WinControls.RoutedEventArgs args)Unknown
 Telerik.WinControls.dll!Telerik.WinControls.RadElement.RaiseBubbleEvent(Telerik.WinControls.RadElement sender, Telerik.WinControls.RoutedEventArgs args)Unknown
 Telerik.WinControls.dll!Telerik.WinControls.RadItem.RaiseBubbleEvent(Telerik.WinControls.RadElement sender, Telerik.WinControls.RoutedEventArgs args)Unknown
 Telerik.WinControls.dll!Telerik.WinControls.RadElement.RaiseRoutedEvent(Telerik.WinControls.RadElement sender, Telerik.WinControls.RoutedEventArgs args)Unknown
 Telerik.WinControls.dll!Telerik.WinControls.RadElement.DoMouseUp(System.Windows.Forms.MouseEventArgs e)Unknown
 Telerik.WinControls.dll!Telerik.WinControls.ComponentInputBehavior.OnMouseUp(System.Windows.Forms.MouseEventArgs e)Unknown
 Telerik.WinControls.dll!Telerik.WinControls.RadControl.OnMouseUp(System.Windows.Forms.MouseEventArgs e)Unknown
 System.Windows.Forms.dll!System.Windows.Forms.Control.WmMouseUp(ref System.Windows.Forms.Message m, System.Windows.Forms.MouseButtons button, int clicks)Unknown
 System.Windows.Forms.dll!System.Windows.Forms.Control.WndProc(ref System.Windows.Forms.Message m)Unknown
 System.Windows.Forms.dll!System.Windows.Forms.ScrollableControl.WndProc(ref System.Windows.Forms.Message m)Unknown
 Telerik.WinControls.dll!Telerik.WinControls.RadControl.WndProc(ref System.Windows.Forms.Message m)Unknown
 System.Windows.Forms.dll!System.Windows.Forms.Control.ControlNativeWindow.OnMessage(ref System.Windows.Forms.Message m)Unknown
 System.Windows.Forms.dll!System.Windows.Forms.Control.ControlNativeWindow.WndProc(ref System.Windows.Forms.Message m)Unknown
 System.Windows.Forms.dll!System.Windows.Forms.NativeWindow.DebuggableCallback(System.IntPtr hWnd, int msg, System.IntPtr wparam, System.IntPtr lparam)Unknown
 [Native to Managed Transition]
 [Managed to Native Transition]
 System.Windows.Forms.dll!System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(System.IntPtr dwComponentID, int reason, int pvLoopData)Unknown
 System.Windows.Forms.dll!System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(int reason, System.Windows.Forms.ApplicationContext context)Unknown
 System.Windows.Forms.dll!System.Windows.Forms.Application.ThreadContext.RunMessageLoop(int reason, System.Windows.Forms.ApplicationContext context)Unknown
 System.Windows.Forms.dll!System.Windows.Forms.Application.Run(System.Windows.Forms.Form mainForm)Unknown
 TelerikWinFormsApp8.exe!TelerikWinFormsApp8.Program.Main() Line 17C#

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Nadya
Telerik team
answered on 15 Dec 2020, 02:56 PM

Hello, Claude,

Thank you for providing the call stack. According to it, it seems that the problem is the 44th line of your form in TelerikWinFormsApp8.exe. I suppose that this is the same project you provided earlier. 

I am using the latest 2020.3.1020 version and does not receive the error that you had. I recorded a small video demonstrating the result on my end. Am I missing something? Do I need to do anything else to reproduce the error when clicking on the arrow button? In order to inspect what causes the error, it is important to reproduce it locally. Thank you in advance for your understanding and cooperation. 

I am looking forward to your reply.

Regards,
Nadya
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Claude
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answered on 18 Dec 2020, 09:59 PM
yes it is.  I know that line 44 errors, but why.  It runs your system.  Works with just a standard  combobox and a switch statement.
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Nadya
Telerik team
answered on 21 Dec 2020, 11:51 AM

Hello, Claude,

According to the exception that you get, it seems that the CurrentRow in EditorControl is null on your end. It becomes null when there is no current row in the grid. I could suggest adding an if-clause and check if the CurrentRow is not null before accessing its Cells collection.

private void RadMultiColumnComboBox1_SelectedValueChanged(object sender, EventArgs e)
{
    if (this.radMultiColumnComboBox1.EditorControl.CurrentRow != null)
    {
        string cc = radMultiColumnComboBox1.EditorControl.CurrentRow.Cells[1].Value.ToString();
    }
}

There is a CurrentRowChanged event as well. You can use it if you want to track every time when the current row has changed.

The current row becomes null if you enter a text into the text box filed and press the Enter key. In this case, if there is no such result in the drop-down list the current row will be null. In this case, I would suggest setting DropDownStyle to DropDownList. Thus, the text box are could not be edited. However, you mentioned that you receive the error when clicking on the dropdown. Can you give these suggestions a try and let me know how they work for you?

I am looking forward to your reply.

Regards,
Nadya
Progress Telerik

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Claude
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answered on 21 Dec 2020, 07:48 PM
Thank you for suggestion.  adding your if statement did the trick.  
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Paul
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answered on 18 Nov 2021, 10:47 AM

We get the same result as Claude only when it is run in 125% DPI. We are using 2021.1.122.40.

Dess | Tech Support Engineer, Principal
Telerik team
commented on 19 Nov 2021, 09:59 AM

Hi, Paul,

I am sorry to hear that you are experiencing any undesired behavior with RadMultiColumnComboBox. However, the provided information is not enough for me to replicate the issue locally and investigate further the precise case. I would recommend you to submit a support ticket from your Telerik account and provide detailed information about the precise case. 

A sample project, demonstrating the exact undesired behavior that you are facing, may save a lot of days and efforts on both sides. That is why it is always greatly appreciated if you simulate the problematic behavior in a runnable project. Then, we would be able to make an adequate analysis of the precise case and think about a suitable solution. This is the most important thing you can do to clearly demonstrate your issue. Replicating your issue is no doubt the most time consuming part, but it's going to play the biggest role in your success at demonstrating your issue clearly the first time. It often feels easier to copy and paste the relevant portions of your code into the ticket. The problem with this approach is that the pieces have to be reviewed by somebody who doesn't know what the entire project is supposed to look like or accomplish.

Thank you in advance for your cooperation.

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Nadya
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Claude
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