如何填充从下拉列表形式的价值？ [英] How to populate a form value from a drop-down?

问题描述

后续从这个问题：如果我想从下拉计算根据用户的选择值下降列表，这个值放到一个表单变量/模型属性，我该怎么做呢？

Follow-on from this question: If I want to calculate a value based on a user's selection from a drop down list, and put that value into a form variable/model property, how do I do that?

推荐答案

说真的，如果我有一个建议给任何ASP.NET MVC开发，这将是：使用视图模型，而忘记了ViewBag /的ViewData 的。在是这样的解决方案，以他的问题/问题99％的情况。

Really, if I had a single advice to give any ASP.NET MVC developer that would be: use a view model and forget about ViewBag/ViewData. In 99% of the cases that is the solution to his questions/problems.

因此​​，这里的最小视图模式，将让你正确地重新present一个下拉列表：

So here's the minimal view model that will allow you to properly represent a dropdown list:

public class MyViewModel
{
    // a scalar property on the view model to hold the selected value
    [DisplayName("item")]
    [Required]
    public string ItemId { get; set; }

    // a collection to represent the list of available options
    // in the drop down
    public IEnumerable<SelectListItem> Items { get; set; }

    ... and some other properties that your view might require
}

再有一个控制器操作将填充并通过这个视图模型到视图：

then have a controller action that will populate and pass this view model to the view:

public ActionResult Index()
{
    var model = new MyViewModel
    {
        // TODO: those values probably come from your database or something
        Items = new[]
        {
            new SelectListItem { Value = "1", Text = "item 1" },
            new SelectListItem { Value = "2", Text = "item 2" },
            new SelectListItem { Value = "3", Text = "item 3" },
        }
    };
    return View(model);
}

，那么你可以有一个相应的强类型的视图可能包含一个表单，并在下拉列表这个视图模型：

then you could have a corresponding strongly typed view to this view model that could contain a form and the dropdown list:

@model MyViewModel
@using (Html.BeginForm())
{
    @Html.LabelFor(x => x.ItemId)
    @Html.DropDownListFor(x => x.ItemId, Model.Items, "--Select One--")
    <button type="submit">OK</button>
}

最后你可以有你的控制器此表格将被提交，并在其内部，您将能够检索从下拉列表中选定的值上的相应动作：

and finally you could have a corresponding action on your controller to which this form will be submitted and inside which you will be able to retrieve the selected value from the dropdown list:

[HttpPost]
public ActionResult Index(MyViewModel model)
{
    // model.ItemId will contain the selected value from the dropdown list
    ...
}

这篇关于如何填充从下拉列表形式的价值？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！