在控制器中返回 Linq 值并将其传递给 View

Question

返回并将所需值传递给视图时遇到问题。我在 LINQPad4 中运行 LINQ 查询，它返回正确的结果。我觉得我在这里遗漏了一些简单的东西。我用这篇文章HERE 作为参考

我收到了

CS1061：“IEnumerable”不包含“FirstName”的定义，并且找不到接受“IEnumerable”类型的第一个参数的扩展方法“FirstName”（您是否缺少 using 指令或程序集引用？）错误. \

当我运行并单步执行代码时，我没有看到任何值，我得到的消息是

Message = "无法创建 'System.Object' 类型的常量值。在此上下文中仅支持原始类型或枚举类型。"

更新

将视图从 @model IEnumerable<Login.Models.EditProfile> 更改为 @model Login.Models.EditProfile 帮助解决了我遇到的 CS1061 错误，至于 LINQ 查询不起作用，请查看以下 Titian 接受的答案。

任何帮助将不胜感激。 如果我可以提供更多信息，请告诉我。

/ 控制器 /

public ActionResult Edit(int? id)
    {


        using (TDBEntities db1 = new TDBEntities())
        {
            var user =  (from a in db1.ExternalUsers
                        join b in db1.ExternalUserEmails on a.ExternalUserID equals b.ExternalUserID
                        join c in db1.ExternalUserPhones on a.ExternalUserID equals c.ExternalUserID
                        where a.ExternalUserID.Equals(id)
                        select new EditProfile {ExternalUserID = a.ExternalUserID, FirstName = a.FirstName, LastName = a.LastName, EmailAddress = b.EmailAddress, PhoneNumber = c.PhoneNumber });

                if (user == null)
                {
                    return HttpNotFound();
                }

            return View(user);
        }
    }

/型号/

    public partial class EditProfile
    {
      public string FirstName { get; set; }
      public string LastName { get; set; }
      public string EmailAddress { get; set; }
      public string PhoneNumber { get; set; }
      public int ExternalUserID { get; set; }

    }

/查看/

@model IEnumerable<Login.Models.EditProfile>
@using Login.Helpers

@{
 ViewBag.Title = "Update Employee";
 }

 <h2></h2>

  @using (Html.BeginForm())
 {
   @Html.AntiForgeryToken()

<div class="form-horizontal">
    <h4>Update Employee</h4>
    <hr />

    <div class="form-group">
        @Html.LabelFor(model => model.FirstName, "First Name:", htmlAttributes: new { @class = "control-label col-md-2" })
        <div class="col-md-10">
            @Html.EditorFor(model => model.FirstName, new { htmlAttributes = new { @class = "form-control" } })
            @Html.ValidationMessageFor(model => model.FirstName, "", new { @class = "text-danger" })
        </div>
    </div>

    <div class="form-group">
        @Html.LabelFor(model => model.LastName, "Last Name:", htmlAttributes: new { @class = "control-label col-md-2" })
        <div class="col-md-10">
            @Html.EditorFor(model => model.LastName, new { htmlAttributes = new { @class = "form-control" } })
            @Html.ValidationMessageFor(model => model.LastName, "", new { @class = "text-danger" })
        </div>
    </div>    

    <div class="form-group">
        @Html.LabelFor(model => model.EmailAddress, "Email Address:", htmlAttributes: new { @class = "control-label col-md-2" })
        <div class="col-md-10">
            @Html.EditorFor(model => model.EmailAddress, new { htmlAttributes = new { @class = "form-control" } })
            @Html.ValidationMessageFor(model => model.EmailAddress, "", new { @class = "text-danger" })
        </div>
    </div>

    <div class="form-group">
        @Html.LabelFor(model => model.PhoneNumber, "Phone Number:", htmlAttributes: new { @class = "control-label col-md-2" })
        <div class="col-md-10">
            @Html.EditorFor(model => model.PhoneNumber, new { htmlAttributes = new { @class = "form-control" } })
            @Html.ValidationMessageFor(model => model.PhoneNumber, "", new { @class = "text-danger" })
        </div>
    </div>

    <div class="form-group">
        <label class="resetPw control-label col-md-2 ">Reset Password</label>            
        <div> @Html.CheckBox("ResetPassword", false, new { @style = "margin: 10px 15px 0;" }) <i>(check to reset)</i></div>
    </div>


    <div class="form-group">
        <div class="col-md-offset-2 col-md-10">
            <input type="submit" value="Save" class="btn btn-default" />
        </div>
    </div>
</div>
}

<div>
    @Html.ActionLink("Back to List", "Index")

Answer 1

您想在查询中添加FirstOrDefault。即使没有值（空结果），Select 也会返回一个值（IQueryable<User> 类型）。如果没有匹配的结果，您实际上想要该结果中的第一个值或 null：

        var user =  (from a in db1.ExternalUsers
                    join b in db1.ExternalUserEmails on a.ExternalUserID equals b.ExternalUserID
                    join c in db1.ExternalUserPhones on a.ExternalUserID equals c.ExternalUserID
                    where a.ExternalUserID == id
                    select new EditProfile {ExternalUserID = a.ExternalUserID, FirstName = a.FirstName, LastName = a.LastName, EmailAddress = b.EmailAddress, PhoneNumber = c.PhoneNumber })
                    .FirstOrDefault();