Last Updated: 23 Jan 2023 09:08 by Stefan

When the user selects a value and then focuses on another component the OnBlur of the ComboBox is not triggered. The issue is reproducible in the Firefox browser (tested with version 109.0).

To reproduce the issue open the following REPL example in the Firefox browser:

Select a value in the first ComboBox and then focus on the second ComboBox. The OnBlur event should trigger.

Last Updated: 20 Jan 2023 08:18 by ADMIN
Release 4.1.0 (15/03/2023)
Created by: Niels Døssing
Comments: 1
Category: ComboBox
Type: Bug Report


EDIT: This issue (of course) relates to the case where the combobox has data selected when rendering.

The clear button of the combobox behaves in a way that I find strange, and which prevents us to get the desired behaviour in our application.

It is easily reproducable with your demo here:


When loading the page there is no clear button, which I think is wrong. Especially since it is not even in the DOM, so it cannot be made visible with styling. When clicking in the field, the clear button appears, and it stays there when changing focus to elsewhere, which seems inconsistent.

In other words, the span of the button (in the red box below) only appears when the combobox has had focus.



Last Updated: 18 Jan 2023 06:55 by ADMIN

I would like the ability to flag elements in a data bound combo that are no longer available as disabled and not selectable.  Had they been previously selected, they still need to show, but should not allow a user to select it again.

I would like a property that can be set when databinding a combo.

For instance when you set the Data, TextField, & ValueField properties, can there also be one for SelectableField (or something) - this could be mapped to a Boolean in the dataset.

If this property isn't used then it defaults to yes (ie they are all selectable), but if it is used, then any items which have this field set to 'no' then they show as a different color (could just be grey) but are not selectable by the user.

If they had previously been selected (prior to being marked as no longer available) then they should show when the record is loaded, but otherwise they are not selectable.

I don't particularly want to write code on click to see if its enabled and then unselect it, I would prefer it to simply be built into the base control.

Is this possible?  Or is there another property already there that does this?

Last Updated: 13 Dec 2022 12:02 by Michal


 iam found "strange" behaviour compared to previous versions in combobox, with custom paging, filtering, valuemapper.

"simple description":
- Do not call OnRead and ValueMapper AFTER clicking/selecting the ITEM in any case(after filtering, or after scrolling...). Do it same way as selecting WITHOUT prior filtering.

Complex test

A sample for testing is here(and comments inside):

How to reproduce:

1 - start = value is PREselected - OK
2 - clear the combobox - OK
2 - input value 40  - slowly do not rush, number by number - OK
3- wait 2 seconds and Click/select item ("Name 401" etc) - NOK
observe the events fired(Exception/info: time - indicates that OnRead was fired again) 

Repeat the same WITHOUT filtering, just scrolling
observe the events fired = looks ok (Exception/info: time)

When selecting item by CLICKING on it(after filtering) looks like those events are fired:
- ValueMapper (why?)
- OnRead again(why again?)
- bind value (ok)
and sometimes ValueMapper again
it depends of "timing"

When selecting item by CLICKING on it:
- BIND the value. Everything is in there(no reason to call OnRead or ValueMapper)

Related, unexpected(video attachment):
Also when working in "real" scenario, AFTER clicking on item AFTER filtering, it returns full MODEL assembly path into to input filed, instead of clicked item
Lets have a list: {Name of the item,Another item,Next item}
entere in combobox/filter "name", results are shown ok, clicked on one and result shuld be ("Name of the item"), after clicking it returns "base model class name"
ie: "inwApp1.Pages.prozam.crm.EdcrmOrg+BaseKeyModel" - you dont want to see this :) .

There is different event orders for those 2 scenarios(it should be the same for both as at point 1) ):
1) when SELECTing item without filtering(just moving with scrollbar down to value 401 (only with onread and virtual paging)) = OK
2) when filtering by value "40" and SELECTing item by clicking on it - NOT OK = it look like this causes the problems and subsequent event calls

Is there any workaround, or new "property" to set? Thanks

Last Updated: 06 Dec 2022 09:39 by ADMIN
Release 4.0.0 (18 Jan 2023) (R1 2023)
Created by: Andrew
Comments: 2
Category: ComboBox
Type: Feature Request

I would like to change the text in the ComboBox dropdown when there is no data in the source collection.

At the moment the only option is through localization for all instances like here.

Last Updated: 25 Oct 2022 22:32 by ADMIN
Created by: Rick
Comments: 1
Category: ComboBox
Type: Feature Request

We are needing a way to display a hierarchy inside the ComboBox.  I don't see any examples on this particular feature, I had found a similar request, but not identical.

Our use case:

We have administrators that manage multiple tenants within our system.  The tenants are part of a hierarchy, the user needs to be able to select a tenant or tenant parent.

I will use hotels as an example:

-Chain 1

--Brand 1

---Property 1

---Property 2

--Brand 2

---Property 3

Our current system that we are migrating controls from has this feature, so I would like to stick as close to this functionality as possible, however; if it is not an option, what control would you suggest as an alternative.

See example (sorry for the redactions)

The core concept is providing a user a choice as part of a form, but layout needs to be organized so that a user can easily navigate.  Top level names are unique, all other names can duplicate since they may share similar naming conventions across different organizations.

An option that may work as an alternative, is invoking a dialog popup and within it having a tree list of the information I need.  I think it could work, but it would certainly break the flow of the form.

Last Updated: 26 Jul 2022 08:11 by ADMIN
I am using a Groupable ComboBox and I would like access to the list of the available groups so that I can create a custom group name sort order.
Last Updated: 12 Jul 2022 07:27 by ADMIN
Release 3.5.0
Created by: Kristofer
Comments: 0
Category: ComboBox
Type: Bug Report

If my browser culture is set to Swedish, I can no longer tab through multiple ComboBoxes.



You can manually add the TabIndex parameter to each ComboBox and set their values to non-negative integers.


Last Updated: 11 Jul 2022 22:29 by Kees

If the AllowCustom parameter is set to true and the OnChange fires during the data load, the value in the OnChange handler is null. Press Enter before the data load ends and the OnChange handler will give null instead of the current input value.

If I enter a text and press enter when there are no items (yet), I expect it to call the OnChange with that text. Even with a static list of zero items (replace 'Read=' with 'Data=' en provide a new List<>()), the OnChange is passed a null value.

If the OnChange fires before the empty dropdown get opened, it passes a null value, if it fires after the empty dropdown opens, it passes the entered text. That doesn't sound logical to me. Why needs the (empty) dropdown to be open before the data gets passed? And if that is necessary, why gets the OnChange fired before the dropdown is opened, and doesn't wait till it is open and then fire with the entered data?

Last Updated: 30 Jun 2022 01:30 by n/a

I would like to use an event that fires only when the user clicks on an item from the dropdown. 



Here is a possible way to achieve this now:

<TelerikComboBox @bind-Value=@SelectedValue
            var currentItem = context as Product;

            <div onclick="@(() => OnClickHandler(currentItem))" style="width:100%">

@code {
    private void OnClickHandler(Product item)
        //the application logic here

    public IEnumerable<Product> ComboBoxData { get; set; }
    public int SelectedValue { get; set; } = 2;

    protected override void OnInitialized()
        List<Product> products = new List<Product>();
        for (int i = 1; i < 10; i++)
            products.Add(new Product()
                    ProductId = i,
                    ProductName = $"Product {i}",
                    UnitPrice = (decimal)(i * 3.14)

        ComboBoxData = products;

    public class Product
        public int ProductId { get; set; }
        public string ProductName { get; set; }
        public decimal UnitPrice { get; set; }

Last Updated: 21 Jun 2022 16:45 by Adam

I have a ComboBox that allows me to select different entities that I want to edit data for.  Some of this data involves selecting other options from ComboBoxes.  When I type in my cascading filterable ComboBox to select an item, its value changes accordingly, but when I change the entity I'm editing, that ComboBox doesn't display the selected value, even though there is a selected value present.

Reproduction: https://blazorrepl.telerik.com/GGYgmlFA45guzWlg06.

Steps to reproduce:

  1. Run the snippet - selected Person is Adam
  2. Start typing "Green" in the Fav Colour ComboBox
  3. Press Enter to select it
  4. Change the Person to John
  5. Fav Colour appears empty while it should display "Yellow"
Last Updated: 31 May 2022 06:54 by ADMIN
Release 3.4.0

In my data, I have multiple identical values for the TextField of the ComboBox. When the user selects one of them and focuses away from the component the selected value changes to the first instance of the items with the same TextFields, although they have different ValueFields.


<TelerikComboBox Data="@myDdlData" 
                 ValueChanged="@((int? id) => ValueChangedHandler(id))" 

@code {
    private List<MyDdlModel> myDdlData { get; set; }

    private void ValueChangedHandler(int? id)
        selectedValue = id;

    public class MyDdlModel
        public int? MyValueField { get; set; }
        public string MyTextField { get; set; }

    int? selectedValue { get; set; }

    protected override void OnInitialized()
        myDdlData = new List<MyDdlModel>()
            new MyDdlModel()
                MyValueField = 1,
                MyTextField = "John Smith"
            new MyDdlModel()
                MyValueField = 2,
                MyTextField = "John Smith"
            new MyDdlModel()
                MyValueField = 3,
                MyTextField = "John Smith"
            new MyDdlModel()
                MyValueField = 4,
                MyTextField = "Alice Jones"
            new MyDdlModel()
                MyValueField = 5,
                MyTextField = "Alice Jones"

Last Updated: 30 May 2022 12:12 by Miroslav


When the user types a value in the input and wishes to navigate to the beginning or end (by pressing Home/End buttons) of the input to make a correction, a value from the popup is actually selected and the value in the input is overridden.


1. Create a ComboBox and enable filtering.

2. Start typing in the input. Popup is opened.

3 Try to navigate in the input via the Home/End buttons. A value from the popup is selected that overrides the value in the input. 

Last Updated: 24 May 2022 13:45 by ADMIN
Created by: Harrison
Comments: 1
Category: ComboBox
Type: Feature Request

Hi Telerik Team,

One of the requirements for my team project is that the ComboBox needs to be sorted in descending order to list dates. We need to sort the groups and the options inside the groups.

Ideally, the ComboBox can have a SortDirection parameter that defines the order as SortAscending or SortDescending, and can display the ComboBox groups and options accordingly.

Last Updated: 06 May 2022 13:23 by ADMIN
Release 3.3.0

A ComboBox is databound via OnRead. It has an initial value, but no data arrives after the first OnRead call. We call Rebind() to fetch data and then it populates, but the component value doesn't show.

Click the button. The ComboBox should show its initial value, but doesn't. A similar scenario worked until version 2.30, when there was no Rebind(), but we set Data directly.

The workaround is to set raise a flag in OnRead and set the value in OnAfterRenderAsync.

@using Telerik.DataSource.Extensions

<TelerikButton OnClick="@BindCombo">Rebind Combo</TelerikButton>

<TelerikComboBox TItem="@ComboItem"

@code {
    string FilterValue { get; set; } = "A";
    int ComboValue { get; set; } = 2;
    bool BindFlag { get; set; }
    bool ShouldResetValue { get; set; }
    IEnumerable<ComboItem> LegacyComboData { get; set; }

    TelerikComboBox<ComboItem, int> ComboRef { get; set; }

    void BindCombo()
        BindFlag = true;

    protected override async Task OnAfterRenderAsync(bool firstRender)
        if (ShouldResetValue)
            // comment out the initially set value above to make the following line work
            ComboValue = 2;

        await base.OnAfterRenderAsync(firstRender);

    async Task OnComboRead(ComboBoxReadEventArgs args)
        if (BindFlag)
            var service = new MyService();

            var data = await service.GetComboItem(FilterValue);
            var result = await data.ToDataSourceResultAsync(args.Request);

            args.Data = result.Data;

            //ShouldResetValue = true;

    public class ComboItem
        public int Id { get; set; }
        public string Code { get; set; }
        public string Text { get; set; }

    public class MyService
        public async Task<IEnumerable<ComboItem>> GetComboItem(string code)
            await Task.Delay(300);

            var data = new[]
                    new ComboItem{ Id = 1, Code = "A", Text = "ValueA1" },
                    new ComboItem{ Id = 2, Code = "A", Text = "ValueA2" },
                    new ComboItem{ Id = 3, Code = "A", Text = "ValueA3" },
                    new ComboItem{ Id = 4, Code = "B", Text = "ValueB4" },
                    new ComboItem{ Id = 5, Code = "B", Text = "ValueB5" },
                    new ComboItem{ Id = 6, Code = "B", Text = "ValueB6" },
                    new ComboItem{ Id = 7, Code = "C", Text = "ValueC7" },
                    new ComboItem{ Id = 8, Code = "C", Text = "ValueC8" },
                    new ComboItem{ Id = 9, Code = "C", Text = "ValueC9" },

            return data.Where(x => x.Code == code).ToList();


Last Updated: 04 May 2022 07:40 by ADMIN
Release 3.3.0

The ComboBox will not display an initial selected item, if the value is equal to the type's default. Applies to integers, guids, etc.

This used to work until version 2.30.

Here is a REPL test page.

If the value type is nullable, a zero int value will work for initial item selection.

Last Updated: 23 Mar 2022 11:06 by ADMIN
Created by: John af P
Comments: 3
Category: ComboBox
Type: Feature Request

Hello, I would like to have a mutiselect dropdown like you have for ajax:


Syncfusion and radzen have this support for blazor :



I know that you have a proposed solution for the MultiSelect component:

CheckBox in Multiselect

But the design of this one is not what I'm after, the box still expands downwards when selecting multiple items and it makes it hard to design a coherent page that does not make the dom "jump around". Also the implementation is cumbersome for more complex objects .

It would be better with a solution like you have for ajax where it just shows the first items that fits and then "+X items".

Last Updated: 22 Mar 2022 09:44 by ADMIN
I have bound the ComboBox to a List<int> and when I set the FIlterable parameter to true, I get an application crash. I would like to be able to filter by integers too. 
Last Updated: 26 Jan 2022 04:08 by ADMIN

See this REPL:


Run the program and scroll so that new data will be requested.  The page variable does not change, so I'm not able to request new data from my datasource.

Last Updated: 16 Dec 2021 06:20 by ADMIN

GitHub Repo - https://github.com/benhysell/BlazorGridPagingIssue

Expected Behavior - In the ComboBox ItemTemplate show the user's email address along with user name

Actual Behavior - Works fine debugging in Visual Studio, however in a published application the browser throws exception and will not display user's email address in the ItemTemplate.

Steps To Reproduce

  • Clone and start debugging application
  • Navigate to https://localhost:5001/createWeather
  • This is a simple form with two ComboBoxes, one for weather data and one for user data
  • In debug the ComboBoxes work as expected, each has an ItemTemplate that shows the desired data.
  • Stop debugging and publish the applicaiton
  • ie -- dotnet publish -o "YOUR DESIRED OUPUT DIRECTORY" -r win-x64 --self-contained
  • Navigate to the output directory and run .\BlazorGrid.Server.exe
  • In the browser navigate to https://localhost:5001/createWeather
  • The page now throws an exception
  • Also notice how the user's email address is no longer shown for the User in the comobobox drop down.


Ran across this in a larger application...I have a class that inherits from Microsoft.AspNetCore.Identity.IdentityUser<Guid> and wanted to display all of my users in a ComboBox with a custom ItemTemplate consisting of the Name and Email.  This works great in debug, however every time I publish/deploy the Email address is not shown.  The example repo is a stripped down version of the larger application reproducing the error.

The application is making an OData call to the backend to retrieve the Users...in the repo we do not goto a database, in the live application we do.  In both instances the user's Email is not shown in the ItemTemplate, even though one can see via the browser's network traffic tab the results from the OData call include the email address for the users.

This issue does not just affect the email property, I was unable to get any of the properties listed on Microsoft.AspNetCore.Identity.IdentityUser<Guid> to render in a published application in the ItemTemplate for the Combobox. 

Note - all of the properties in Microsoft.AspNetCore.Identity.IdentityUser<Guid> are marked as 'virtual'.  I attempted to re-create this issue with a different class, in the repo I used the WeatherForecast class and created a virtual TemperatureK property...this however worked in debug and release without issue.  One can see this in the OData Weather Forecasts ComboBox on the same page, https://localhost:5001/createWeather.

1 2 3