在ASP.NET MVC中填充DropDownlist [英] populating a DropDownlist in ASP.NET MVC

问题描述

我正在学习ASP.NET MVC.在处理下拉列表时，我遇到了一个小问题.

I'm learning ASP.NET MVC. I had a small problem when dealing with dropdownlist.

这就是我在控制器中所做的

This is what I did in controller

List<Int32> myList = new List<Int32>();
var a = (from m in datacontext.services
                 select m.ServiceID);
myList = a.ToList();
ViewData["ServiceID"] = new SelectList((IEnumerable<SelectListItem>)
                                a.ToList(), "ServiceID", "ServiceID");

在视图中

 @Html.DropDownListFor(model => model.ServiceID, ViewData["ServiceID"] as SelectList)

这会导致错误

无法转换类型为'System.Collections.Generic.List 1[System.Int32]' to type 'System.Collections.Generic.IEnumerable 1 [System.Web.Mvc.SelectListItem]'的对象."

Unable to cast object of type 'System.Collections.Generic.List1[System.Int32]' to type 'System.Collections.Generic.IEnumerable1[System.Web.Mvc.SelectListItem]'."

如何解决?

用查询处理下拉列表的最佳方法是什么?

What's the best way to deal with populating dropdownlist with a query?

推荐答案

强制转换中存在错误.

要解决此问题，您可以执行以下操作:

To fix you can do this:

var a = datacontext.services.Select(arg => new { ServiceID = arg.ServiceID }).ToList();
ViewData["ServiceID"] = new SelectList(a, "ServiceID", "ServiceID");

或者这个:

var a = datacontext.services.Select(arg => arg.ServiceID).ToList();
ViewData["ServiceID"] = new SelectList(a);

在您的代码中a是整数列表.无法将其强制转换为SelectListItem的列表.

In your code a is the list of integers. It cannot be cast into the list of SelectListItem.

旁注: myList变量未在您的代码中使用.

Side note: myList variable is not used in your code.

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