ant-design-blazor/components/calendar/internal/CalendarHeader.razor

@namespace AntDesign
@inherits AntDomComponentBase
@using AntDesign.Internal

<div class="@(PrefixCls)-header"
     style="@Style"
     id="@Id"
     @ref="@Ref">
    @{
        int startYear = Calendar.Value.AddYears(-10).Year;
        int endYear = Calendar.Value.AddYears(10).Year;

        if (Calendar.ValidRange != null)
        {
            startYear = Calendar.ValidRange[0].Year;
            endYear = Calendar.ValidRange[1].Year;
        }

        string yearFormat = Calendar.CultureInfo.GetDateLocale().YearFormat;
    }
    <Select class=@($"{PrefixCls}-year-select")
            Size=@(Calendar.FullScreen ? AntSizeLDSType.Default : AntSizeLDSType.Small)
            DefaultValue=@($"{Calendar.Value.Year}") 
            OnChange="async (value, option) => await OnSelectYear(value.AsT0)">
        @for (int year = startYear; year <= endYear; year++)
        {
            DateTime yearDate = new DateTime(year, 1, 1);
            <SelectOption @key="@yearDate.Year" Value=@($"{yearDate.Year}")>
                @(yearDate.ToString(yearFormat, Calendar.CultureInfo))
            </SelectOption>
        }
    </Select>

    @if (Calendar.Mode == DatePickerType.Month)
    {
        int startMonth = 1;
        int endMonth = 12;

        if (Calendar.ValidRange != null)
        {
            startMonth = Calendar.Value.Year == Calendar.ValidRange[0].Year ? Calendar.ValidRange[0].Month : startMonth;
            endMonth = Calendar.Value.Year == Calendar.ValidRange[1].Year ? Calendar.ValidRange[1].Month : endMonth;
        }

        string monthFormat = Calendar.CultureInfo.GetDateLocale().MonthFormat;

        <Select class=@($"{PrefixCls}-month-select")
                Size=@(Calendar.FullScreen ? AntSizeLDSType.Default : AntSizeLDSType.Small)
                DefaultValue=@($"{Calendar.Value.Month}") 
                OnChange="async (value, option) => await OnSelectMonth(value.AsT0)">
            @for (int month = startMonth; month <= endMonth; month++)
            {
                DateTime monthDate = new DateTime(1, month, 1);
                <SelectOption @key="@monthDate.Month" Value=@($"{monthDate.Month}")>
                    @(monthDate.ToString(monthFormat, Calendar.CultureInfo))
                </SelectOption>
            }
        </Select>
    }
    
    <RadioGroup class=@($"{PrefixCls}-mode-switch")
                Size=@(Calendar.FullScreen ? AntSizeLDSType.Default : AntSizeLDSType.Small)
                Value="@Calendar.Mode"
                OnChange="OnModeChange">
        <Radio RadioButton Value="@DatePickerType.Month">@(Calendar.CultureInfo.GetDateLocale().Month)</Radio>
        <Radio RadioButton Value="@DatePickerType.Year">@(Calendar.CultureInfo.GetDateLocale().Year)</Radio>
    </RadioGroup>
</div>

@code
{
    [CascadingParameter(Name = "PrefixCls")]
    public string PrefixCls { get; set; }

    [CascadingParameter(Name = "Calendar")]
    public Calendar Calendar { get; set; }

    private DateTime currentDate;
    private bool hasChangeYear = true;

    protected override void OnInitialized()
    {
        base.OnInitialized();

        currentDate = Calendar.Value;
    }

    private void OnModeChange(string value)
    {
        Calendar.ChangePickerType(value);
    }

    private async Task OnSelectYear(string value)
    {
        int year = Convert.ToInt32(value);
        await Calendar.ChangeValue(DateHelper.CombineNewDate(Calendar.Value, year: year));
    }

    private async Task OnSelectMonth(string value)
    {
        int month = Convert.ToInt32(value);
        await Calendar.ChangeValue(DateHelper.CombineNewDate(Calendar.Value, month: month));
    }
}