ASP.NET Core MVC Select List Attributes

ASP.NET Core library which gives the ability to specify select lists via Model Attributes at both Type and Property levels. The select lists can be used to populate dropdowns but also as an IEnumerable collection to loop through in views.

Features:

1. Uses expression syntax such as "{Id} - {Description} - {Cost}" for SelectListItem text/value rather than a single property. I recommend using nameof(Class.Property) for compile time safety.
2. Uses HtmlHelper.Display to render text/value rather than reflection used in SelectList and MultiSelectList. The advantage being you get model property formatting.
3. When used with services.AddSelectListAttributes() select lists (where selectListId = null) are automatically bound to SelectTagHelper and can be overriden by setting ViewBag.Property or ViewData["Property"] to IEnumerable<SelectListItem>. Usually SelectTagHelper doesn't allow passing IEnumerable<SelectListItem> in the ViewBag/ViewData.
4. Ability to define additional select lists by specifying selectListId.
5. Ability to extend by inheriting from SelectListAttribute. Have access to IServiceProvider on the SelectListContext.
6. Not limited to model properties. Can also be applied to types.
7. Tag helpers for bootstrap 4 radio and checkbox lists.
8. EF Core Value Converters for persisting lists as CSV or Json.

Advantages:

1. Keep select list logic with model, controllers slim and views for render only.
2. Implementing radio and checkbox lists in ASP.NET Core can be time consuming.
3. Could be exended to expose select lists via API in a generic fashion. e.g /api/customers/lookup/{selectListId} or /api/customers/age/lookup/{selectListId}

Installation

NuGet

PM> Install-Package AspNetCore.Mvc.SelectList

.Net CLI

> dotnet add package AspNetCore.Mvc.SelectList

Usage

services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_2)
.AddMvcSelectListAttributes();

Model Example

public enum MailPreference
{
	[Display(Name = "Email")]
	Email,
	[Display(Name = "Mail")]
	Mail,
	[Display(Name = "None")]
	None
}

public class Subscription
{
	public string Id { get; set; }

	public int Order { get; set; }

	public string Description { get; set; }

	[DisplayFormat(DataFormatString = "{0:C2}")]
	public decimal Cost { get; set; }
}

[SelectListDb(typeof(AppDbContext), typeof(Customer), OrderByProperty = nameof(Customer.Id))]
public class Customer
{
	[HiddenInput]
	public Guid Id { get; set; }

	[Required]
	[Display(Name = "Name")]
	public string Name { get; set; }

	[Display(Name = "Age")]
	[SelectListOptions("18-30","31-50","50+")]
	[SelectListOptions("35-70", "70-80", "80+", SelectListId = "List2")]
	public string Age { get; set; }

	[Display(Name = "Susbcription")]
	[SelectListDb(typeof(AppDbContext), typeof(Subscription), "{" + nameof(Subscription.Description) + "} - {" + nameof(Subscription.Cost) + "}", OrderByProperty = nameof(Subscription.Order), OrderByType = "asc" )]
	public string SubscriptionId { get; set; }

	[Display(Name = "Susbcription 2")]
	[SelectListDb(typeof(AppDbContext), typeof(Subscription), "SELECT * FROM Subscriptions WHERE Description = {0}", new object[] { "Standard" }, "{" + nameof(Subscription.Description) + "} - {" + nameof(Subscription.Cost) + "}")]
	public string SubscriptionId2 { get; set; }

	[Display(Name = "Susbcription")]
	[SelectListDb(typeof(AppDbContext), typeof(Subscription), "{" + nameof(Subscription.Description) + "} - {" + nameof(Subscription.Cost) + "}", OrderByProperty = nameof(Subscription.Order), OrderByType = "asc")]
	[SelectListDbWhereEquals(nameof(Subscription.Description), "Standard")]
	public string SubscriptionId3 { get; set; }

	[Display(Name = "File")]
	[SelectListFile("files")]
	public string File { get; set; }

	[Display(Name = "Folder")]
	[SelectListFolder("files")]
	public string Folder { get; set; }

	[Display(Name = "File2")]
	[SelectListFile("wwwroot")]
	public string File2 { get; set; }

	[Display(Name = "Status")]
	[SelectListDb(typeof(AppDbContext), typeof(Status), "{" + nameof(Status.Description) + "} - {" + nameof(Status.Id) + "}", OrderByType = "asc")]
	public int StatusId { get; set; }

	[Display(Name = "Mail Preference")]
	[SelectListEnum]
	public MailPreference MailPreference { get; set; }

	[Display(Name = "Country")]
	[SelectListCountry]
	public string CountryCode { get; set; }

	[CsvDb]
	[LimitOptionsMinMax(1,2)]
	[Display(Name = "Checkbox List")]
	[SelectListEnum]
	public List<MailPreference> CheckboxValues { get; set; } = new List<MailPreference>();

	[CsvDb]
	[LimitOptionsMin(1)]
	[Display(Name = "Checkbox Button List")]
	[SelectListCountry]
	public List<string> CheckboxButtonValues { get; set; } = new List<string>();

	[Required]
	[Display(Name = "Radio List")]
	[SelectListEnum]
	public MailPreference RadioValue { get; set; }

	[Required]
	[Display(Name = "Radio Button List")]
	[SelectListEnum]
	public MailPreference RadioButtonValue { get; set; }

	[Display(Name = "Yes/No Radio Button List with no default")]
	[SelectListYesNo]
	public bool? YesNo { get; set; }

	[Display(Name = "True/False Radio Button List with no default")]
	[SelectListTrueFalse]
	public bool? TrueFalse { get; set; }

	[Display(Name = "Yes/No Radio Button List with default")]
	[SelectListYesNo]
	public bool YesNoDefault { get; set; }

	[Display(Name = "True/False Radio Button List with default")]
	[SelectListTrueFalse]
	public bool TrueFalseDefault { get; set; }

	[Display(Name = "Yes Only")]
	[SelectListYes]
	public bool Yes { get; set; }

	[Display(Name = "No Only")]
	[SelectListNo]
	public bool No { get; set; }

	[Display(Name = "True Only")]
	[SelectListTrue]
	public bool True { get; set; }

	[Display(Name = "False Only")]
	[SelectListFalse]
	public bool False { get; set; }
}

View Example

@model Customer

<form asp-controller="Customer" asp-action="Update" method="post">
	<input asp-for="Id" />
	<label asp-for="Name"></label>
	<input asp-for="Name">
	<span asp-validation-for="Name" class="text-danger"></span>
	<br />
	<label asp-for="Age"></label>
	<select asp-for="Age" asp-items="@(Html.SelectListFor(model => model.Age, "List2"))"></select>
	<span asp-validation-for="Age" class="text-danger"></span>
	<br />
	<label asp-for="SubscriptionId"></label>
	<select asp-for="SubscriptionId"></select>
	<span asp-validation-for="SubscriptionId" class="text-danger"></span>
	<br />
	<label asp-for="SubscriptionId2"></label>
	<select asp-for="SubscriptionId2"></select>
	<span asp-validation-for="SubscriptionId2" class="text-danger"></span>
	<br />
	<label asp-for="SubscriptionId3"></label>
	<select asp-for="SubscriptionId3"></select>
	<span asp-validation-for="SubscriptionId3" class="text-danger"></span>
	<br />
	<label asp-for="File"></label>
	<select asp-for="File"></select>
	<span asp-validation-for="File" class="text-danger"></span>
	<br />
	<label asp-for="Folder"></label>
	<select asp-for="Folder"></select>
	<span asp-validation-for="Folder" class="text-danger"></span>
	<br />
	<label asp-for="File2"></label>
	<select asp-for="File2"></select>
	<span asp-validation-for="File2" class="text-danger"></span>
	<br />
	<label asp-for="StatusId"></label>
	<select asp-for="StatusId"></select>
	<span asp-validation-for="StatusId" class="text-danger"></span>
	<br />
	<label asp-for="MailPreference"></label>
	<select asp-for="MailPreference"></select>
	<span asp-validation-for="MailPreference" class="text-danger"></span>
	<br />
	<label asp-for="CountryCode"></label>
	<select asp-for="CountryCode"></select>
	<span asp-validation-for="CountryCode" class="text-danger"></span>
	<br />
	<label asp-for="RadioValue"></label>
	<radio-list asp-for="RadioValue"></radio-list>
	<span asp-validation-for="RadioValue" class="text-danger"></span>
	<br />
	<label asp-for="CheckboxValues"></label>
	<checkbox-list asp-for="CheckboxValues"></checkbox-list>
	<span asp-validation-for="CheckboxValues" class="text-danger"></span>
	<br />
	<label asp-for="RadioButtonValue"></label>
	<radio-button-list asp-for="RadioButtonValue"></radio-button-list>
	<span asp-validation-for="RadioButtonValue" class="text-danger"></span>
	<br />
	<label asp-for="CheckboxButtonValues"></label>
	<checkbox-button-list asp-for="CheckboxButtonValues" class="btn btn-outline-primary mr-2 mb-2 btn-lg"></checkbox-button-list>
	<span asp-validation-for="CheckboxButtonValues" class="text-danger"></span>
	<br />
	<label asp-for="YesNo"></label>
	<radio-button-list asp-for="YesNo"></radio-button-list>
	<span asp-validation-for="YesNo" class="text-danger"></span>
	<br />
	<label asp-for="TrueFalse"></label>
	<radio-button-list asp-for="TrueFalse"></radio-button-list>
	<span asp-validation-for="TrueFalse" class="text-danger"></span>
	<br />
	<label asp-for="YesNoDefault"></label>
	<radio-button-list asp-for="YesNoDefault"></radio-button-list>
	<span asp-validation-for="YesNoDefault" class="text-danger"></span>
	<br />
	<label asp-for="TrueFalseDefault"></label>
	<radio-button-list asp-for="TrueFalseDefault"></radio-button-list>
	<span asp-validation-for="TrueFalseDefault" class="text-danger"></span>
	<br />
	<label asp-for="Yes"></label>
	<checkbox-button-list asp-for="Yes"></checkbox-button-list>
	<span asp-validation-for="Yes" class="text-danger"></span>
	<br />
	<label asp-for="No"></label>
	<checkbox-button-list asp-for="No"></checkbox-button-list>
	<span asp-validation-for="No" class="text-danger"></span>
	<br />
	<label asp-for="True"></label>
	<checkbox-button-list asp-for="True"></checkbox-button-list>
	<span asp-validation-for="True" class="text-danger"></span>
	<br />
	<label asp-for="False"></label>
	<checkbox-button-list asp-for="False"></checkbox-button-list>
	<span asp-validation-for="False" class="text-danger"></span>
	<br />
	<button type="submit">Add/Update</button>
</form>

@section Scripts {
    <partial name="_ValidationScriptsPartial" />
}

@addTagHelper *, AspNetCore.Mvc.SelectList

Get List

@foreach (var item in await Html.SelectListForModelTypeAsync<Customer>())
{
	@item.Html.DisplayFor(c => c.Name);
	<br />
}

Filter by Id

{
	var item = await Html.SelectListForModelTypeAsync<Customer>(new object[]{"ecf1f87a-ce11-471d-abae-735d23c91256"}).FirstOrDefault();
	@item.Html.DisplayFor(c => c.Name);
}

Override Attribute Select List

[HttpGet]
public IActionResult Edit()
{
	ViewBag.File = new List<SelectListItem>() { };

	return View("Edit", _db.Customers.Find(_customerId));
}

Custom Select List Attribute

public class SelectListCustomAttribute : SelectListAttribute
{
	public SelectListCustomAttribute()
	{

	}

	protected override Task<IEnumerable<SelectListItem>> GetSelectListItemsAsync(SelectListContext context)
	{
		var db = context.HttpContext.RequestServices.GetRequiredService<AppContext>();
		return new List<SelectListItem>();
	}     
}

Select List Attributes

Attribute	Description
SelectListAttribute	Base class for extension
SelectListOptionsAttribute	Specify Options
SelectListDbAttribute	Specify DbContext and ModelType
SelectListDbWhereEqualsAttribute	Specify DbContext Where Property Equals Clause
SelectListEnumAttribute	Automatically calls Html.GetEnumSelectList()
SelectListFileAttribute	Specify physical, Content Root virtual or Web Root virtual path such as "~/files/"
SelectListFolderAttribute	Specify physical, Content Root virtual or Web Root virtual path such as "~/files/"
SelectListCountryAttribute	Lists Countries
SelectListTrueFalseAttribute	True and False options binding to boolean or boolean?
SelectListTrueAttribute	True option binding to boolean or boolean?
SelectListFalseAttribute	False option binding to boolean or boolean?
SelectListYesNoAttribute	Yes and No options binding to boolean or boolean?
SelectListYesttribute	Yes option binding to boolean or boolean?
SelectListNoAttribute	No options binding to boolean or boolean?

Tag Helpers

TagHelper	Description
radio-list	Outputs radio list. 1 option can be selected.
checkbox-list	Outputs checkbox list. 0 or more options can be selected.
radio-button-list	Outputs radio list buttons. class attribute styles the buttons. 1 option can be selected.
checkbox-button-list	Outputs checkbox list buttons. class attribute styles the buttons. 0 or more options can be selected.

Db Converter Attributes

public class AppDbContext : DbContext
{
	public AppDbContext(DbContextOptions<AppDbContext> options)
		: base(options)
	{
		
	}

	protected override void OnModelCreating(ModelBuilder modelBuilder)
	{
		modelBuilder.AddCsvValues();
		modelBuilder.AddJsonValues();
	}
}

Attribute	Description
CsvDb	Saves Array, List, Collections to Db as Csv
JsonDb	Saves Object to Db as Json

Authors

• Dave Ikin - davidikin45

License

This project is licensed under the MIT License