Question

我只是想将值绑定到下拉列表控件。我看不到任何例子，但它对我不起作用。请找到我的代码和错误，并帮我解决这个问题。

//我的模特

public class SubjectModel
{
    public int selectedid {get;set;}
    public List<SelectListItem> ddllist{get;set;}
    public SubjectModel()
    {
        ddllist = new List<SelectListItem>();
    }
}

//我的控制器

public ActionResult DropDownTest()
{

    SubjectModel model = new SubjectModel();
    model.ddllist.Add(new SelectListItem { Text = "Physics", Value = "1" });
    model.ddllist.Add(new SelectListItem { Text = "Chemistry", Value = "2" });
    model.ddllist.Add(new SelectListItem { Text = "Mathematics", Value = "3" });

    model.selectedid = 0;

    return View(model);        
}

//我的观点

<!DOCTYPE HTML PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<%@Page Language="C#" Inherits="System.Web.Mvc.ViewPage<DopDownBinding.Models.SubjectModel>"%>    

<html>
<head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width,initial-scale=1.0" />
    <title>DropDownBinding</title>
</head>
<body>
    <section id="ip">

        <p>
            <label for="timezone">Subjects</label>

            @Html.DropDownListFor(model => model.selectedid, new SelectList(Model.ddllist, "SubCategoryId", "SubCategoryName", Model.selectedid))
        </p>
    </section>
</body>

执行此操作时出现此错误。

表达式树可能不包含动态操作

我是MVC的新手，如果出现问题，请帮我纠正。谢谢

Answer 1

由于ddllist类中的SubjectModel属性为List<SelectListItem>，因此您无需为new SelectList(Model.ddllist, "SubCategoryId", "SubCategoryName", Model.selectedid)辅助对象的第二个参数执行@Html.DropDownListFor。

更改此语法

@Html.DropDownListFor(
    model => model.selectedid, 
             new SelectList(
                 Model.ddllist, 
                 "SubCategoryId", 
                 "SubCategoryName", 
                 Model.selectedid))

到这个

@Html.DropDownListFor(model => model.selectedid, Model.ddllist)

您还需要删除第二行

<%@Page 
    Language="C#" 
    Inherits="System.Web.Mvc.ViewPage<DopDownBinding.Models.SubjectModel>"%>

并将此语法添加到第一行

@model DopDownBinding.Models.SubjectModel

Answer 2

你在Razor中的下拉应该是

//Model.ddllist is selectlist for your dropdown
@Html.DropDownListFor(model => model.selectedid, Model.ddllist)

DropDownList绑定错误

2 个答案: