ASP.NET Core 2.2 - Filtering Entities

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This article will describe how to filter a list of entities. I will assume you have created a new ASP.NET Core 2.2 Razor Pages project. I won't use Identity or Individual User Accounts.

The FREE ASP.NET Core 6.0 - Demos And Utilities Project includes a Table Functions Demo. Access to the source code is free for registered users at Manage > Assets.

I will try to add value to many great articles about filtering by using a dropdown and radio button group to select entities.

Edit Index.cshtml.cs, add the filtering properties and queries:
private readonly FoodDbContext _context;

public IndexModel(FoodDbContext context)
    _context = context;

public int Count { get; set; }

public class RadioButtonProperties
    public string Name { get; set; }
    public string ElementId { get; set; }
    public bool IsSelected { get; set; }

public List<RadioButtonProperties> ColdStoreRadioButtons { get; set; }

[Display(Name = "Store Cold")]
public string SelectedColdStoreRadio { get; set; }

[Display(Name = "Food Type")]
public FoodType SelectedFoodType { get; set; }

public IList<SelectListItem> FoodTypes { get; set; } = new List<SelectListItem>();

public IList<Food> Foods { get; set; } = new List<Food>();

public void OnGet(FoodType selectedFoodType = FoodType.All, string selectedColdStoreRadio = "All")
    SelectedFoodType = selectedFoodType;
    FoodTypes = new List<SelectListItem>();
    var options = Enum.GetValues(typeof(FoodType));
    foreach (var type in options)
        FoodTypes.Add(new SelectListItem() { Text = type.ToString(), Value = type.ToString() });

    ColdStoreRadioButtons = new List<RadioButtonProperties>()
        new RadioButtonProperties() { Name = "All", ElementId = "ColdStoreRadioButtonAll" },
        new RadioButtonProperties() { Name = "Yes", ElementId = "ColdStoreRadioButtonYes" },
        new RadioButtonProperties() { Name = "No", ElementId = "ColdStoreRadioButtonNo" }

    SelectedColdStoreRadio = selectedColdStoreRadio;

    var foodQuery = _context.Foods.AsQueryable();

    switch (SelectedFoodType)
        case FoodType.Fruit:
            foodQuery = _context.Foods.Where(f => f.FoodType == FoodType.Fruit).AsQueryable();
        case FoodType.Vegtable:
            foodQuery = _context.Foods.Where(f => f.FoodType == FoodType.Vegtable).AsQueryable();
        case FoodType.Other:
            foodQuery = _context.Foods.Where(f => f.FoodType == FoodType.Other).AsQueryable();

    switch (SelectedColdStoreRadio)
        case "Yes":
            foodQuery = foodQuery.Where(f => f.ColdStore == true).AsQueryable();
        case "No":
            foodQuery = foodQuery.Where(f => f.ColdStore == false).AsQueryable();

    Foods = foodQuery.ToList();

    Count = Foods.Count();

Edit Index.cshtml, add the dropdown and radio buttons:
<div class="row pt-1 mb-2">
    <div class="col-12 mb-1">
        <a asp-route-currentPage=""
           class="btn btn-primary">Reset</a>
        <h4 class="d-inline ml-2">
            Count = @Model.Count.ToString()
<div class="row mb-2">
    <div class="col-12 col-md-4 col-lg-4">
        <h5 class="">@Html.DisplayNameFor(model => model.SelectedFoodType)</h5>
        <form class="" id="FoodTypeForm" method="get">
            <input type="hidden" asp-for="SelectedColdStoreRadio" />
            <select class="form-control mb-1" asp-for="SelectedFoodType"
    <div class="col-12 col-md-5 col-lg-6 mb-2">
        <h5 class="">@Html.DisplayNameFor(model => model.SelectedColdStoreRadio)</h5>
        @for (var i = 0; i < Model.ColdStoreRadioButtons.Count(); i++)
            <div class="custom-control custom-radio custom-control-inline">
                <input type="radio" value="@Model.ColdStoreRadioButtons[i].Name" class="custom-control-input"
                       id="@Model.ColdStoreRadioButtons[i].ElementId" asp-for="SelectedColdStoreRadio" />
                <label class="custom-control-label" for="@Model.ColdStoreRadioButtons[i].ElementId">

Notice the Enum.GetValues(typeof(FoodType)).

Edit Index.cshtml, add the JavaScript:
function getFoodType() {

// After DOMContentLoaded
var coldStoreRadioButtons = document.querySelectorAll('[name="SelectedColdStoreRadio"]');
var rbl = coldStoreRadioButtons.length;
for (var rb = 0; rb < rbl; rb++) {
    coldStoreRadioButtons[rb].addEventListener('click', function (event) {
        var selectFoodType = document.querySelector('#SelectedFoodType');
        var foodType = selectFoodType.options[selectFoodType.selectedIndex].text;
        var coldStore = document.querySelector('input[name="SelectedColdStoreRadio"]:checked').value;
        location.replace('/index?currentPage=1' +
            '&selectedFoodType=' + foodType +
            '&selectedColdStoreRadio=' + coldStore);

Build, run and test.

Filtered Table.
Update 12/30/2021

Announced the ASP.NET Core 6.0 - Demos And Utilities Project. Updated articles, asset and topic links.

Ken Haggerty
Created 08/25/19
Updated 08/28/22 02:17 GMT

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Article Tags:

EF Core JavaScript
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