Calendar

The Calendar component provides a Blazor implementation of the ASP.NET Web Forms Calendar control, enabling users to select dates and navigate through months.

Original Microsoft documentation: https://docs.microsoft.com/en-us/dotnet/api/system.web.ui.webcontrols.calendar?view=netframework-4.8

Features Supported in Blazor

• SelectedDate property for single date selection
• SelectedDates collection for multi-date selection (read-only)
• VisibleDate property to set the displayed month
• SelectionMode (None, Day, DayWeek, DayWeekMonth)
• Two-way binding with @bind-SelectedDate
• Month/year navigation with next/previous buttons
• OnSelectionChanged event when a date is selected
• OnDayRender event for customizing individual days
• OnVisibleMonthChanged event when the month changes
• Customizable display options:
• ShowTitle - Show/hide title bar
• ShowDayHeader - Show/hide day name headers
• ShowGridLines - Show/hide grid borders
• ShowNextPrevMonth - Show/hide navigation
• Day name formatting (DayNameFormat: Full, Short, FirstLetter, FirstTwoLetters, Shortest)
• Title formatting (TitleFormat: Month, MonthYear)
• Customizable navigation text (NextMonthText, PrevMonthText, SelectWeekText, SelectMonthText)
• First day of week configuration (FirstDayOfWeek)
• Cell padding and spacing options
• TableItemStyle sub-components for rich styling (preferred):
• <CalendarDayStyle> - Regular day cells
• <CalendarTitleStyle> - Title bar
• <CalendarDayHeaderStyle> - Day name headers
• <CalendarTodayDayStyle> - Today's date cell
• <CalendarSelectedDayStyle> - Selected date cell
• <CalendarOtherMonthDayStyle> - Days from adjacent months
• <CalendarWeekendDayStyle> - Weekend day cells
• <CalendarNextPrevStyle> - Next/previous navigation links
• <CalendarSelectorStyle> - Week/month selector column
• Each TableItemStyle sub-component supports: CssClass, BackColor, ForeColor, BorderColor, BorderStyle, BorderWidth, Height, Width, HorizontalAlign, VerticalAlign, Wrap, Font-Bold, Font-Italic, Font-Size, Font-Name, etc.
• Legacy CSS string properties (deprecated but still functional):
• TitleStyleCss, DayHeaderStyleCss, DayStyleCss, TodayDayStyleCss, SelectedDayStyleCss, OtherMonthDayStyleCss, WeekendDayStyleCss, NextPrevStyleCss, SelectorStyleCss
• Visible property to show/hide the calendar
• CssClass for custom CSS styling
• ToolTip for accessibility

Web Forms Features NOT Supported

• DayRender event cannot add custom controls to cells (Blazor limitation)
• Caption and CaptionAlign properties not implemented
• TodaysDate property not implemented (use DateTime.Today)
• UseAccessibleHeader not implemented

Style Properties Migration

Individual style objects (DayStyle, TitleStyle, etc.) from Web Forms are now supported via TableItemStyle sub-components such as <CalendarDayStyle>, <CalendarTitleStyle>, etc. The older CSS string properties (DayStyleCss, TitleStyleCss, etc.) still work but are deprecated. See the migration example below.

Web Forms Declarative Syntax

<asp:Calendar
    CellPadding="2"
    CellSpacing="0"
    DayNameFormat="Short|Full|FirstLetter|FirstTwoLetters|Shortest"
    FirstDayOfWeek="Sunday|Monday|Tuesday|Wednesday|Thursday|Friday|Saturday|Default"
    ID="string"
    NextMonthText="string"
    NextPrevFormat="ShortMonth|FullMonth|CustomText"
    OnDayRender="DayRenderEventHandler"
    OnSelectionChanged="EventHandler"
    OnVisibleMonthChanged="MonthChangedEventHandler"
    PrevMonthText="string"
    SelectedDate="DateTime"
    SelectionMode="None|Day|DayWeek|DayWeekMonth"
    SelectMonthText="string"
    SelectWeekText="string"
    ShowDayHeader="True|False"
    ShowGridLines="True|False"
    ShowNextPrevMonth="True|False"
    ShowTitle="True|False"
    TitleFormat="Month|MonthYear"
    VisibleDate="DateTime"
    runat="server">
    <DayStyle />
    <TodayDayStyle />
    <SelectedDayStyle />
    <OtherMonthDayStyle />
    <WeekendDayStyle />
    <TitleStyle />
    <NextPrevStyle />
    <DayHeaderStyle />
    <SelectorStyle />
</asp:Calendar>

Blazor Declarative Syntax

<Calendar
    CellPadding="2"
    CellSpacing="0"
    DayNameFormat="Short|Full|FirstLetter|FirstTwoLetters|Shortest"
    FirstDayOfWeek="Sunday|Monday|Tuesday|Wednesday|Thursday|Friday|Saturday"
    ID="string"
    NextMonthText="string"
    OnDayRender="DayRenderEventHandler"
    OnSelectionChanged="EventHandler"
    OnVisibleMonthChanged="MonthChangedEventHandler"
    PrevMonthText="string"
    @bind-SelectedDate="dateVariable"
    SelectionMode="None|Day|DayWeek|DayWeekMonth"
    SelectMonthText="string"
    SelectWeekText="string"
    ShowDayHeader="True|False"
    ShowGridLines="True|False"
    ShowNextPrevMonth="True|False"
    ShowTitle="True|False"
    TitleFormat="Month|MonthYear"
    VisibleDate="DateTime"
    CssClass="string">

    @* TableItemStyle sub-components (preferred) *@
    <CalendarDayStyle CssClass="string" BackColor="string" ForeColor="string" />
    <CalendarTitleStyle CssClass="string" BackColor="string" ForeColor="string" Font-Bold="true" />
    <CalendarDayHeaderStyle CssClass="string" BackColor="string" ForeColor="string" />
    <CalendarTodayDayStyle CssClass="string" BackColor="string" ForeColor="string" />
    <CalendarSelectedDayStyle CssClass="string" BackColor="string" ForeColor="string" />
    <CalendarOtherMonthDayStyle CssClass="string" ForeColor="string" />
    <CalendarWeekendDayStyle CssClass="string" BackColor="string" />
    <CalendarNextPrevStyle CssClass="string" ForeColor="string" />
    <CalendarSelectorStyle CssClass="string" BackColor="string" />

</Calendar>

Deprecated CSS String Properties

The following properties still work but are deprecated. Use the TableItemStyle sub-components above instead: TitleStyleCss, DayStyleCss, TodayDayStyleCss, SelectedDayStyleCss, OtherMonthDayStyleCss, WeekendDayStyleCss, DayHeaderStyleCss, NextPrevStyleCss, SelectorStyleCss

Usage Examples

Basic Calendar

@page "/calendar-demo"

<h3>Select a Date</h3>
<Calendar @bind-SelectedDate="selectedDate" />
<p>You selected: @selectedDate.ToShortDateString()</p>

@code {
    private DateTime selectedDate = DateTime.Today;
}

Calendar with Week Selection

<Calendar SelectionMode="DayWeek" 
          @bind-SelectedDate="weekStart"
          OnSelectionChanged="HandleSelection" />

@code {
    private DateTime weekStart = DateTime.Today;

    private void HandleSelection()
    {
        // User selected a week starting at weekStart
    }
}

Calendar with Month Selection

<Calendar SelectionMode="DayWeekMonth" 
          @bind-SelectedDate="monthStart" />

@code {
    private DateTime monthStart = DateTime.Today;
}

Customized Calendar

<Calendar ShowGridLines="true"
          DayNameFormat="Full"
          TitleFormat="MonthYear"
          FirstDayOfWeek="DayOfWeek.Monday"
          NextMonthText="Next →"
          PrevMonthText="← Prev"
          @bind-SelectedDate="selectedDate" />

Styled Calendar (using TableItemStyle sub-components)

<Calendar @bind-SelectedDate="selectedDate">
    <CalendarTitleStyle BackColor="#007bff" ForeColor="White" Font-Bold="true" />
    <CalendarSelectedDayStyle BackColor="#28a745" ForeColor="White" />
    <CalendarTodayDayStyle BackColor="#ffc107" Font-Bold="true" />
    <CalendarWeekendDayStyle BackColor="#f8f9fa" />
    <CalendarOtherMonthDayStyle ForeColor="#ccc" />
    <CalendarDayHeaderStyle BackColor="#e9ecef" Font-Bold="true" />
    <CalendarNextPrevStyle ForeColor="White" />
</Calendar>

Styled Calendar (legacy CSS string properties — deprecated)

<Calendar CssClass="my-calendar"
          TitleStyleCss="calendar-title"
          SelectedDayStyleCss="selected-date"
          TodayDayStyleCss="today-date"
          WeekendDayStyleCss="weekend-date"
          @bind-SelectedDate="selectedDate" />

<style>
.my-calendar {
    border: 1px solid #ccc;
}
.calendar-title {
    background-color: #007bff;
    color: white;
    font-weight: bold;
}
.selected-date {
    background-color: #28a745;
    color: white;
}
.today-date {
    background-color: #ffc107;
    font-weight: bold;
}
.weekend-date {
    background-color: #f8f9fa;
}
</style>

Calendar with Event Handlers

<Calendar @bind-SelectedDate="selectedDate"
          OnSelectionChanged="HandleSelectionChanged"
          OnVisibleMonthChanged="HandleMonthChanged"
          OnDayRender="HandleDayRender" />

<p>Selection count: @selectionCount</p>
<p>Current month: @currentMonth.ToString("MMMM yyyy")</p>

@code {
    private DateTime selectedDate = DateTime.Today;
    private int selectionCount = 0;
    private DateTime currentMonth = DateTime.Today;

    private void HandleSelectionChanged()
    {
        selectionCount++;
    }

    private void HandleMonthChanged(CalendarMonthChangedArgs args)
    {
        currentMonth = args.CurrentMonth;
    }

    private void HandleDayRender(CalendarDayRenderArgs args)
    {
        // Disable Sundays
        if (args.Date.DayOfWeek == DayOfWeek.Sunday)
        {
            args.IsSelectable = false;
        }

        // Disable past dates
        if (args.Date < DateTime.Today)
        {
            args.IsSelectable = false;
        }
    }
}

Display Specific Month

<Calendar VisibleDate="specificMonth"
          @bind-SelectedDate="selectedDate" />

@code {
    private DateTime specificMonth = new DateTime(2024, 12, 1);
    private DateTime selectedDate = DateTime.Today;
}

Read-Only Calendar (No Selection)

<Calendar SelectionMode="None" 
          VisibleDate="@DateTime.Today" />

Migration Notes

From Web Forms to Blazor

Web Forms:

<asp:Calendar ID="Calendar1" 
              runat="server" 
              OnSelectionChanged="Calendar1_SelectionChanged">
    <SelectedDayStyle BackColor="Blue" ForeColor="White" />
</asp:Calendar>

protected void Calendar1_SelectionChanged(object sender, EventArgs e)
{
    DateTime selected = Calendar1.SelectedDate;
}

Blazor:

<Calendar @bind-SelectedDate="selectedDate"
          OnSelectionChanged="HandleSelectionChanged">
    <CalendarSelectedDayStyle BackColor="Blue" ForeColor="White" />
</Calendar>

@code {
    private DateTime selectedDate = DateTime.Today;

    private void HandleSelectionChanged()
    {
        // Date is available in selectedDate variable
    }
}

Migrating from CSS String Properties to TableItemStyle

If you previously used the CSS string properties, migrate to the new sub-components:

Before (deprecated):

<Calendar TitleStyleCss="calendar-title"
          SelectedDayStyleCss="selected-date"
          TodayDayStyleCss="today-date"
          WeekendDayStyleCss="weekend-date"
          DayHeaderStyleCss="header-style"
          @bind-SelectedDate="selectedDate" />

After (preferred):

<Calendar @bind-SelectedDate="selectedDate">
    <CalendarTitleStyle CssClass="calendar-title" />
    <CalendarSelectedDayStyle CssClass="selected-date" />
    <CalendarTodayDayStyle CssClass="today-date" />
    <CalendarWeekendDayStyle CssClass="weekend-date" />
    <CalendarDayHeaderStyle CssClass="header-style" />
</Calendar>

Best Practice

The TableItemStyle sub-components also support inline style properties like BackColor, ForeColor, and Font-Bold — matching the Web Forms <DayStyle>, <TitleStyle>, etc. child elements. This makes migration from Web Forms markup even more direct.

Key Differences

1. Style Properties: Use TableItemStyle sub-components (<CalendarDayStyle>, <CalendarTitleStyle>, etc.) for a direct match to Web Forms style child elements, or use CssClass for CSS-based styling. Legacy CSS string properties (DayStyleCss, etc.) are deprecated.
2. DayNameFormat / TitleFormat: Use enum values directly — DayNameFormat="Full", DayNameFormat="Short", DayNameFormat="FirstLetter", DayNameFormat="FirstTwoLetters", DayNameFormat="Shortest" for day names; TitleFormat="Month" or TitleFormat="MonthYear" for the title.
3. Event Handlers: Use EventCallback pattern instead of event delegates
4. Data Binding: Use @bind-SelectedDate for two-way binding
5. Day Rendering: The OnDayRender event provides day information but cannot inject custom HTML into cells

Common Scenarios

Date Range Picker

<h4>Start Date</h4>
<Calendar @bind-SelectedDate="startDate" />

<h4>End Date</h4>
<Calendar @bind-SelectedDate="endDate" OnDayRender="HandleEndDateDayRender" />

@code {
    private DateTime startDate = DateTime.Today;
    private DateTime endDate = DateTime.Today.AddDays(7);

    private void HandleEndDateDayRender(CalendarDayRenderArgs args)
    {
        // Disable dates before start date
        if (args.Date < startDate)
        {
            args.IsSelectable = false;
        }
    }
}

Holiday Calendar

<Calendar @bind-SelectedDate="selectedDate"
          OnDayRender="HandleHolidayRender"
          WeekendDayStyleCss="weekend"
          OtherMonthDayStyleCss="other-month" />

@code {
    private DateTime selectedDate = DateTime.Today;
    private List<DateTime> holidays = new List<DateTime>
    {
        new DateTime(2024, 1, 1),  // New Year
        new DateTime(2024, 7, 4),  // Independence Day
        new DateTime(2024, 12, 25) // Christmas
    };

    private void HandleHolidayRender(CalendarDayRenderArgs args)
    {
        if (holidays.Contains(args.Date))
        {
            args.IsSelectable = false;
        }
    }
}

See Also

• TextBox - For alternative date input using TextBoxMode.Date
• Button - For submitting forms with selected dates
• Panel - For grouping calendar with related controls