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Scheduler Events

Updated on Oct 12, 2026

This article explains the events available in the Telerik Scheduler for Blazor:

CUD Events

To implement appointment editing, the scheduler exposes the OnCreate, OnDelete and OnUpdate events. They let you propagate the changes the user makes in the UI to the view model and to the data storage. You can read mode in the Appointment Editing article.

OnModelInit

The OnModelInit event fires before editing and adding new item in the component. The event allows you to:

  • bind the component to a class that has no parameterless constructor

  • bind the component to an interface

  • bind the component to an abstract class

To achieve the desired behavior you can provide an instance of the model that the component is bound to in the OnModelInit event handler.

The different use-cases of the OnModelInit event

RAZOR
@* Bind the Scheduler to a class without a parameterless constructor *@

<TelerikScheduler Data="@Appointments"
                  OnModelInit="@OnModelInitHandler"
                  OnUpdate="@UpdateAppointment"
                  OnCreate="@AddAppointment"
                  OnDelete="@DeleteAppointment"
                  OnEdit="@EditHandler" OnCancel="@CancelHandler"
                  AllowCreate="true" AllowDelete="true" AllowUpdate="true"
                  @bind-Date="@StartDate" Height="600px" @bind-View="@CurrView">
    <SchedulerViews>
        <SchedulerDayView StartTime="@DayStart" />
        <SchedulerWeekView StartTime="@DayStart" />
        <SchedulerMultiDayView StartTime="@DayStart" NumberOfDays="10" />
    </SchedulerViews>
</TelerikScheduler>

@code {
    // sample data and scheduler settings
    public SchedulerView CurrView { get; set; } = SchedulerView.Week;
    public DateTime StartDate { get; set; } = new DateTime(2019, 12, 2);
    public DateTime DayStart { get; set; } = new DateTime(2000, 1, 1, 8, 0, 0); //the time portion is important

    private SchedulerAppointment OnModelInitHandler()
    {
        return new SchedulerAppointment(Guid.NewGuid(), String.Empty, String.Empty, new DateTime(), new DateTime(), false, String.Empty, null, null);
    }

    List<SchedulerAppointment> Appointments { get; set; }

    async Task UpdateAppointment(SchedulerUpdateEventArgs args)
    {
        SchedulerAppointment item = (SchedulerAppointment)args.Item;

        // perform actual data source operations here through your service
        await MyService.Update(item);

        // update the local view-model data with the service data
        await GetSchedulerData();
    }

    async Task AddAppointment(SchedulerCreateEventArgs args)
    {
        SchedulerAppointment item = (SchedulerAppointment)args.Item;

        // perform actual data source operations here through your service
        await MyService.Create(item);

        // update the local view-model data with the service data
        await GetSchedulerData();
    }

    async Task DeleteAppointment(SchedulerDeleteEventArgs args)
    {
        SchedulerAppointment item = (SchedulerAppointment)args.Item;

        // perform actual data source operations here through your service
        await MyService.Delete(item);

        // update the local view-model data with the service data
        await GetSchedulerData();

        // see the comments in the service mimic method below.
    }

    //Handlers for application logic flexibility
    void EditHandler(SchedulerEditEventArgs args)
    {
        SchedulerAppointment item = (SchedulerAppointment)args.Item;
        if (!args.IsNew) // an edit operation, otherwise - an insert operation
        {
            // you can prevent opening an item for editing based on a condition
            if (item.Title.Contains("vet", StringComparison.InvariantCultureIgnoreCase))
            {
                args.IsCancelled = true;
            }
        }
        else
        {
            // new appointment
            DateTime SlotStart = args.Start; // the start of the slot the user clicked
            DateTime SlotEnd = args.End; // the start of the slot the user clicked
            bool InsertInAllDay = args.IsAllDay; // whether the user started insertion in the All Day row
        }
    }

    void CancelHandler(SchedulerCancelEventArgs args)
    {
        // you can know when a user wanted to modify an appointment but decided not to
        // the model you get contains the new data from the edit form so you can see what they did
        SchedulerAppointment item = (SchedulerAppointment)args.Item;
    }


    public class SchedulerAppointment
    {
        public Guid Id { get; set; }
        public string Title { get; set; }
        public string Description { get; set; }
        public DateTime Start { get; set; }
        public DateTime End { get; set; }
        public bool IsAllDay { get; set; }
        public string RecurrenceRule { get; set; }
        public List<DateTime> RecurrenceExceptions { get; set; }
        public Guid? RecurrenceId { get; set; }

        public SchedulerAppointment(Guid id, string title, string description, DateTime start, DateTime end, bool allDay, string recurrance, List<DateTime> exceptions, Guid? recurrenceId)
        {
            Id = id;
            Title = title;
            Description = description;
            Start = start;
            End = end;
            IsAllDay = allDay;
            RecurrenceRule = recurrance;
            RecurrenceExceptions = exceptions;
            RecurrenceId = recurrenceId;
        }
    }

    async Task GetSchedulerData()
    {
        Appointments = await MyService.Read();
    }

    protected override async Task OnInitializedAsync()
    {
        await GetSchedulerData();
    }

    // the following static class mimics an actual data service that handles the actual data source
    // replace it with your actual service through the DI, this only mimics how the API can look like and works for this standalone page
    public static class MyService
    {
        private static List<SchedulerAppointment> _data { get; set; } = new List<SchedulerAppointment>()
        {
            new SchedulerAppointment(Guid.NewGuid(), "Board meeting", "Q4 is coming to a close, review the details.",new DateTime(2019, 12, 5, 10, 00, 0),new DateTime(2019, 12, 5, 11, 30, 0), false, String.Empty, null, null),
            new SchedulerAppointment(Guid.NewGuid(), "Vet visit", "The cat needs vaccinations and her teeth checked.",new DateTime(2019, 12, 2, 11, 30, 0),new DateTime(2019, 12, 2, 12, 0, 0), false, String.Empty, null, null),
            new SchedulerAppointment(Guid.NewGuid(), "Planning meeting", "Kick off the new project.", new DateTime(2019, 12, 6, 9, 30, 0), new DateTime(2019, 12, 6, 12, 45, 0), false, String.Empty, null, null),
            new SchedulerAppointment(Guid.NewGuid(), "Trip to Hawaii", "An unforgettable holiday!", new DateTime(2019, 11, 27), new DateTime(2019, 12, 05), true, String.Empty, null, null),
            new SchedulerAppointment(Guid.NewGuid(), "Morning run", "Some time to clear the head and exercise.", new DateTime(2019, 11, 27, 9, 0, 0), new DateTime(2019, 11, 27, 9, 30, 0), false,  "FREQ=WEEKLY;BYDAY=MO,TU,WE,TH,FR", null, null)
        };

        public static async Task Create(SchedulerAppointment itemToInsert)
        {
            itemToInsert.Id = Guid.NewGuid();
            _data.Insert(0, itemToInsert);
        }

        public static async Task<List<SchedulerAppointment>> Read()
        {
            return await Task.FromResult(_data);
        }

        public static async Task Update(SchedulerAppointment itemToUpdate)
        {
            var index = _data.FindIndex(i => i.Id == itemToUpdate.Id);
            if (index != -1)
            {
                _data[index] = itemToUpdate;
            }
        }

        public static async Task Delete(SchedulerAppointment itemToDelete)
        {
            if (itemToDelete.RecurrenceId != null)
            {
                // a recurrence exception was deleted, you may want to update
                // the rest of the data source - find an item where theItem.Id == itemToDelete.RecurrenceId
                // and remove the current exception date from the list of its RecurrenceExceptions
            }

            if (!string.IsNullOrEmpty(itemToDelete.RecurrenceRule) && itemToDelete.RecurrenceExceptions?.Count > 0)
            {
                // a recurring appointment was deleted that had exceptions, you may want to
                // delete or update any exceptions from the data source - look for
                // items where theItem.RecurrenceId == itemToDelete.Id
            }

            _data.Remove(itemToDelete);
        }
    }
}

OnItemClick

The OnItemClick event fires when the user clicks on an appointment in the Scheduler. It provides a SchedulerItemClickEventArgs object to the event handler and you can get the Item property and cast it to your own model. If you set the ShouldRender property to true, the component will re-render. This can be useful if you need to change the Scheduler parameters or state during the event execution and especially if you need to execute async logic in the event handler.

Use the OnItemClick event for the scheduler

Example
View Source
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OnItemDoubleClick

The OnItemDoubleClick event fires when the user double clicks on an appointment in the Scheduler. It provides a SchedulerItemDoubleClickEventArgs object to the event handler and you can get the Item property and cast it to your own model. If you set the ShouldRender property to true, the component will re-render. This can be useful if you need to change the Scheduler parameters or state during the event execution and especially if you need to execute async logic in the event handler.

Use the OnItemDoubleClick event for the scheduler

Example
View Source
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OnItemContextMenu

The OnItemContextMenu event fires when the user right clicks on an appointment in the Scheduler. It provides a SchedulerItemContextMenuEventArgs object to the event handler and you can get the Item property and cast it to your own model. If you set the ShouldRender property to true, the component will re-render. This can be useful if you need to change the Scheduler parameters or state during the event execution and especially if you need to execute async logic in the event handler.

Use the OnItemContextMenu event for the scheduler

Example
View Source
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OnItemRender

The OnItemRender event fires when an appointment is going to be rendered in the scheduler. It fires one for every appointment, including all-day appointments that span several days/slots, and the class is rendered on all elements.

Through its event arguments you can get the Item to cast it to your model type and to set the Class that will render on the appointment wrapping element. This lets you customize the appearance of the entire appointment, not just the contents of its template.

Customize the appearance of the scheduler appointments by adding custom CSS classes to them conditionally

Example
View Source
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OnCellRender

The OnCellRender event fires upon rendering of each slot cell. It allows you to set a custom CSS class to the cell, based on business logic.

The handler receives an argument of type SchedulerCellRenderEventArgs which exposes the following fields:

FieldTypeDescription
ClassstringThe CSS class that will be applied to the cell.
IsAllDayboolWhether the slot is inside the AllDay row/column.
ResourcesList<KeyValuePair<string, object>The resources that are associated with the column/row. Applicable when the Scheduler uses both - resources and grouping. Needed to differentiate between the same dates within different groups.
StartDateTimeThe slot start time.
EndDateTimeThe slot end time.

Customize certain Scheduler slots by handling the OnCellRender event

Example
View Source
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DateChanged

The DateChanged event fires when the user navigates to another date in the scheduler. For a view whose start is determined by outside factors and not only by the Date parameter (the week view), the event argument may not always be the start time of the range, but a date contained within the range. You could also use this event to load only appointments from the view's range which can be a performance optimization technique if you have a very large number of appointments.

Handle the DateChanged event

Example
View Source
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The event is an EventCallback. It can be synchronous and return void, or asynchronous and return async Task. Do not use async void.

ViewChanged

The ViewChanged event fires when the user chooses a new View. You can read more about the navigation options the user has in the Navigation article.

Handle the ViewChanged event.

Example
View Source
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The event is an EventCallback. It can be synchronous and return void, or asynchronous and return async Task. Do not use async void.

See Also

In this article
CUD EventsOnModelInitOnItemClickOnItemDoubleClickOnItemContextMenuOnItemRenderOnCellRenderDateChangedViewChangedSee Also
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