If there is a possibility of an item existing in the options with that value, you may want to consider making the property nullable instead.The best websites out there will always follow the best trends and standards. Therefore if you have an item in the list of options with this value, it will be selected by default.
When the page is executed, it will acquire the default value for its type, in this case 0. The SelectedTag property is not nullable. Now the generated HTML shows that the item with a value of "5" has been selected: TagOptions = new SelectList(_tagService.GetTags(), nameof(Tag.TagId), nameof(Tag.TagName))
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This next example shows how to use the System.DayOfWeek enumeration to present the days of the week as option values, and assumes that the PageModel has a property of the correct type called DayOfWeek: public DayOfWeek DayOfWeek The Html.GetEnumSelectList method makes it easy to use an enumeration as the data source for a select list. Options = new SelectList(dictionary, "Key", "Value") Var dictionary = (k => k.AuthorId, v => v.Name) Here's a version that takes a Dictionary: Options = new SelectList(context.Authors, nameof(Author.AuthorId), nameof(Author.Name)) You can create a SelectList from any collection but you need to specify the DataTextField and DataValueField values for the select tag helper to bind the options correctly: This property is then available to be assigned to the items attribute in the select tag helper: You can project data from an Entity Framework context to a collection of SelectListItem like this: The first two of these are strings, and theSelected` property is a boolean. The SelectListItem class hasText ,Value andSelected properties. The following examples will cover the most common of those. There are many ways to shape data for consumption as options in a select tag helper. It will generate option elements for each item. The items attribute expects a collection of SelectListItem objects, a SelectList object or an enumeration that provide the options for the select list. If the PageModel property passed to the for attribute is some kind of collection, the tag helper assumes that you want to allow the user to make multiple selections and will add the multiple attribute to the rendered select element. The for attribute takes the name of the PageModel property that represents the selected value, or values. The select tag helper has two attributes: for and items. If you are interested in learning how to use the HTML helpers, check the "Further Reading" section at the end. This guide will only focus on the tag helper. Razor offers two ways to generate select lists: the select tag helper and the DropDownList (and DropDownListFor) Html Helpers, which are artefacts inherited from pre-ASP.NET Core versions of the MVC framework. posted value is assigned to the Number property automatically The recommended approach, however is to add a suitable property to the PageModel and to allow model binding to apply the posted value to the property: public IndexModel : PageModel You can access the value by passing the key as an indexer to the Request.Form collection: var number = Request.Form This is used as the key for any selected value(s) when a form is submitted. The following example is used to illustrate the main features of these two HTML elements: They are rendered in HTML as a select element, which acts as a container for a number of option elements, each representing an available choice. Select lists or DropDown lists are used in a Razor Pages form to enable users to select zero or more predefined options. Managing Security With ASP.NET Identity.
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