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Refresh custom filter menu (#2595)
* kb(Grid): add kb for refreshing a custom filter menu * chore: update example and apply suggested changes * chore: bold text with strong tag
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‎knowledge-base/grid-custom-filter-menu.md‎

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---
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title: How to Refresh Filter Menu After Programmatic Changes
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description: Learn how to refresh filter menu context after programmatic changes with a custom component
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type: how-to
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page_title: How to Refresh Filter Menu After Programmatic Changes
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slug: grid-kb-custom-filter-menu
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tags: blazor, grid, filter, filtermenu
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res_type: kb
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ticketid: 1669381
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---
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## Environment
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<table>
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<tbody>
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<tr>
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<td>Product</td>
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<td>Grid for Blazor</td>
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</tr>
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</tbody>
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</table>
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## Description
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When using the TelerikGrid in Blazor applications, it's common to implement a custom `FilterMenu` for enhanced filtering capabilities. However, integrating a Telerik UI for Blazor component that is responsible for the dynamic Grid filtering based on user input does not work as expected. For example, the [AutoComplete]({%slug autocomplete-overview%}) component does not consider the selection from the dropdown list of `StringOperators` within the [`FilterMenuTemplate`]({%slug grid-templates-filter%}#filter-menu-template).
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This knowledge base article also answers the following questions:
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- How to integrate AutoComplete with `StringOperators` in a TelerikGrid `FilterMenuTemplate`?
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- How to refresh the contents of `FilterMenuTemplate` in a TelerikGrid?
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- How to refresh a `FilterMenuTemplate` after programmatic changes?
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## Solution
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To achieve the desired behavior, encapsulate the content of the `FilterMenuTemplate` in a separate Razor component and refresh this component upon selection change in the dropdown list. Below is an example demonstrating this approach:
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<div class="skip-repl"></div>
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````Home.razor
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@using Telerik.DataSource
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<TelerikGrid Data="@Countries"
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FilterMode="GridFilterMode.FilterMenu"
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PageSize="25">
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<GridColumns>
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<GridColumn Field="@(nameof(Country.CountryName))">
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<FilterMenuTemplate>
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<CustomFilterMenu @bind-FilterOperator="@FilterOperator"
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@bind-SelectedCountry="@SelectedCountry"
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Countries="@Countries"
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FilterOperators="@FilterOperators" />
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</FilterMenuTemplate>
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<FilterMenuButtonsTemplate Context="filterContext">
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<TelerikButton OnClick="@(async _ => await FilterAsync(filterContext))" Class="k-button-solid-primary">Filter</TelerikButton>
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<TelerikButton OnClick="@(async _ => await ClearFilterAsync(filterContext))">Clear</TelerikButton>
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</FilterMenuButtonsTemplate>
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</GridColumn>
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</GridColumns>
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</TelerikGrid>
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@code {
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private IEnumerable<StringFilterOperator> FilterOperators { get; set; } = Enum.GetValues(typeof(StringFilterOperator)).Cast<StringFilterOperator>().ToList();
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private StringFilterOperator FilterOperator { get; set; } = StringFilterOperator.StartsWith;
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private string SelectedCountry { get; set; } = null!;
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private async Task FilterAsync(FilterMenuTemplateContext filterContext)
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{
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AddFilterDescriptor(filterContext.FilterDescriptor);
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await filterContext.FilterAsync();
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}
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private async Task ClearFilterAsync(FilterMenuTemplateContext filterContext)
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{
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SelectedCountry = string.Empty;
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AddFilterDescriptor(filterContext.FilterDescriptor);
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filterContext.FilterDescriptor.FilterDescriptors.Clear();
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await filterContext.ClearFilterAsync();
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}
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private void AddFilterDescriptor(CompositeFilterDescriptor filterDescriptor)
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{
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var model = string.Empty;
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object? value = null;
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value = SelectedCountry;
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model = nameof(Country.CountryName);
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filterDescriptor.FilterDescriptors.Clear();
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filterDescriptor.FilterDescriptors.Add(new FilterDescriptor(model, Telerik.DataSource.FilterOperator.IsEqualTo, value));
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}
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private List<Country> Countries { get; set; } = new List<Country>()
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{
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new Country { Id = 1, CountryName = "Albania" },
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new Country { Id = 2, CountryName = "Andorra" },
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new Country { Id = 3, CountryName = "Armenia" },
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new Country { Id = 4, CountryName = "Austria" },
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new Country { Id = 5, CountryName = "Azerbaijan" },
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new Country { Id = 6, CountryName = "Belarus" },
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new Country { Id = 7, CountryName = "Belgium" },
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new Country { Id = 8, CountryName = "Bosnia & Herzegovina" },
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new Country { Id = 9, CountryName = "Bulgaria" },
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new Country { Id = 10, CountryName = "Croatia" },
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new Country { Id = 11, CountryName = "Cyprus" },
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new Country { Id = 12, CountryName = "Czech Republic" },
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new Country { Id = 13, CountryName = "Denmark" },
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new Country { Id = 14, CountryName = "Estonia" },
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new Country { Id = 15, CountryName = "Finland" },
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new Country { Id = 16, CountryName = "France" },
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new Country { Id = 17, CountryName = "Georgia" },
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new Country { Id = 18, CountryName = "Germany" },
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new Country { Id = 19, CountryName = "Greece" },
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new Country { Id = 20, CountryName = "Hungary" },
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new Country { Id = 21, CountryName = "Iceland" },
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new Country { Id = 22, CountryName = "Ireland" },
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new Country { Id = 23, CountryName = "Italy" },
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new Country { Id = 24, CountryName = "Kosovo" },
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new Country { Id = 25, CountryName = "Latvia" },
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new Country { Id = 26, CountryName = "Liechtenstein" },
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new Country { Id = 27, CountryName = "Lithuania" },
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new Country { Id = 28, CountryName = "Luxembourg" },
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new Country { Id = 29, CountryName = "Macedonia" },
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new Country { Id = 30, CountryName = "Malta" },
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new Country { Id = 31, CountryName = "Moldova" },
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new Country { Id = 32, CountryName = "Monaco" },
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new Country { Id = 33, CountryName = "Montenegro" },
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new Country { Id = 34, CountryName = "Netherlands" },
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new Country { Id = 35, CountryName = "Norway" },
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new Country { Id = 36, CountryName = "Poland" },
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new Country { Id = 37, CountryName = "Portugal" },
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new Country { Id = 38, CountryName = "Romania" },
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new Country { Id = 39, CountryName = "Russia" },
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new Country { Id = 40, CountryName = "San Marino" },
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new Country { Id = 41, CountryName = "Serbia" },
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new Country { Id = 42, CountryName = "Slovakia" },
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new Country { Id = 43, CountryName = "Slovenia" },
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new Country { Id = 44, CountryName = "Spain" },
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new Country { Id = 45, CountryName = "Sweden" },
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new Country { Id = 46, CountryName = "Switzerland" },
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new Country { Id = 47, CountryName = "Turkey" },
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new Country { Id = 48, CountryName = "Ukraine" },
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new Country { Id = 49, CountryName = "United Kingdom" },
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new Country { Id = 50, CountryName = "Vatican City" }
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};
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public class Country
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{
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public int Id { get; set; }
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public string CountryName { get; set; } = null!;
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}
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}
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````
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````CustomFilterMenu.razor
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@using Telerik.DataSource
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@using Microsoft.AspNetCore.Components
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@using static Home
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<label for="filterOperator"><strong>Select Filter Operator for the AutoComplete:</strong></label>
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<TelerikDropDownList Value="@FilterOperator"
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ValueChanged="@( (StringFilterOperator newValue) => OnFilterOperatorChanged(newValue) )"
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Id="filterOperator"
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Data="@FilterOperators"
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Width="200px">
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<DropDownListSettings>
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<DropDownListPopupSettings Height="auto"></DropDownListPopupSettings>
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</DropDownListSettings>
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</TelerikDropDownList>
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<label for="autocomplete"><strong>Filter the Grid by Country:</strong></label>
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<TelerikAutoComplete ScrollMode="@DropDownScrollMode.Virtual"
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Value="@SelectedCountry"
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ValueChanged="@( (string selectedCountry) => HandleSelectedCountryChange(selectedCountry) )"
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TItem="Country"
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Data="@Countries"
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ValueField="CountryName"
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Width="200px"
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PageSize="20"
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Filterable="true"
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ItemHeight="35"
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FilterOperator="@FilterOperator">
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<AutoCompleteSettings>
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<AutoCompletePopupSettings Height="auto" MaxHeight="200px" MinHeight="75px" />
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</AutoCompleteSettings>
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</TelerikAutoComplete>
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@code {
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[Parameter] public EventCallback<StringFilterOperator> FilterOperatorChanged { get; set; }
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[Parameter] public EventCallback<string> SelectedCountryChanged { get; set; }
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[Parameter] public StringFilterOperator FilterOperator { get; set; }
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[Parameter] public string SelectedCountry { get; set; } = string.Empty;
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[Parameter] public IEnumerable<Country> Countries { get; set; } = Enumerable.Empty<Country>();
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[Parameter] public IEnumerable<StringFilterOperator> FilterOperators { get; set; } = null!;
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private async Task OnFilterOperatorChanged(StringFilterOperator newValue)
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{
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FilterOperator = newValue;
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await FilterOperatorChanged.InvokeAsync(newValue);
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}
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private async Task HandleSelectedCountryChange(string newValue)
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{
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SelectedCountry = newValue;
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await SelectedCountryChanged.InvokeAsync(newValue);
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}
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}
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````
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## See Also
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- [DropDownList Overview]({%slug components/dropdownlist/overview%})
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- [Grid FilterMenu Documentation]({%slug grid-filter-menu%})
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- [Feedback Portal - Expose a Method to Refresh the FilterMenu](https://feedback.telerik.com/blazor/1584289-expose-a-method-to-refresh-the-filtermenu-from-the-code)

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