MVC变量未在视图中显示

Question

I have 4 related classes which I am attempting to display information on but the value of the bottom level class attributes are not being displayed in the view despite the value being available when debugging it is never being transferred to the page my code is as follows:

CONTROLLER

// GET: MarketMessages
public ActionResult Index()
{
    var test = db.MarketMessage.Where(m => m.messageType == "300S")
    .Include(m => m.messageType300S
    .Select(mt => mt.Meter
    .Select(r => r.RegisterLevelInformation )))
    .ToList();

    return View(test);
}

VIEW

@foreach (var item in Model) {
    <tr>
        <td>
            @Html.DisplayFor(modelItem => item.CreatedOn)
        </td>
        <td>
            @Html.DisplayFor(modelItem => item.messageType)
        </td>
        <td>
            @Html.DisplayFor(modelItem => item.VersionNumber)
        </td>
        <td>
            @Html.DisplayFor(modelItem => item.MarketTimestamp)
        </td>
        <td>
            @Html.DisplayFor(modelItem => item.TxRefNbr)
        </td>
        <td>
            @Html.DisplayFor(modelItem => item.Sender)
        </td>
        <td>
            @Html.DisplayFor(modelItem => item.Recipient)
        </td>
        <td>
            @Html.DisplayFor(modelItem => item.alertFlag)
        </td>
        <td>
            @Html.DisplayFor(modelItem => item.fileName)
        </td>
        <td>
            @Html.DisplayFor(modelItem => item.IsDeleted)
        </td>
        <td>
            @foreach (var m in item.messageType300S.Select(m => m.Meter).FirstOrDefault())
            {
                @Html.Display(m.SerialNumber)
            }
        </td>
        <td>
            @Html.ActionLink("Edit", "Edit", new { id=item.MarketMessageID }) |
            @Html.ActionLink("Details", "Details", new { id=item.MarketMessageID }) |
            @Html.ActionLink("Delete", "Delete", new { id=item.MarketMessageID })
        </td>
    </tr>
}

MODEL TOP LEVEL

namespace BillingEngine.DAL
{
    using System;
    using System.Collections.Generic;
    using System.ComponentModel.DataAnnotations;
    using System.ComponentModel.DataAnnotations.Schema;
    using System.Data.Entity.Spatial;

    [Table("MarketMessage")]
    public partial class MarketMessage
    {
        [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA2214:DoNotCallOverridableMethodsInConstructors")]
        public MarketMessage()
        {
            messageType300 = new HashSet<messageType300>();
            messageType300S = new HashSet<messageType300S>();
            messageType300W = new HashSet<messageType300W>();
            messageType305 = new HashSet<messageType305>();
        }

        public int MarketMessageID { get; set; }

        public DateTime CreatedOn { get; set; }

        [Required]
        [StringLength(4)]
        public string messageType { get; set; }

        [Required]
        [StringLength(8)]
        public string VersionNumber { get; set; }

        public DateTime MarketTimestamp { get; set; }

        [Required]
        [StringLength(35)]
        public string TxRefNbr { get; set; }

        [Required]
        [StringLength(3)]
        public string Sender { get; set; }

        [Required]
        [StringLength(3)]
        public string Recipient { get; set; }

        [StringLength(10)]
        public string alertFlag { get; set; }

        [StringLength(50)]
        public string fileName { get; set; }

        public bool IsDeleted { get; set; }

        [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA2227:CollectionPropertiesShouldBeReadOnly")]
        public virtual ICollection<messageType300> messageType300 { get; set; }

        [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA2227:CollectionPropertiesShouldBeReadOnly")]
        public virtual ICollection<messageType300S> messageType300S { get; set; }

        [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA2227:CollectionPropertiesShouldBeReadOnly")]
        public virtual ICollection<messageType300W> messageType300W { get; set; }

        [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA2227:CollectionPropertiesShouldBeReadOnly")]
        public virtual ICollection<messageType305> messageType305 { get; set; }
    }
}

MODEL LEVEL 2

namespace BillingEngine.DAL
{
    using System;
    using System.Collections.Generic;
    using System.ComponentModel.DataAnnotations;
    using System.ComponentModel.DataAnnotations.Schema;
    using System.Data.Entity.Spatial;

    public partial class messageType300S
    {
        [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA2214:DoNotCallOverridableMethodsInConstructors")]
        public messageType300S()
        {
            Meter = new HashSet<Meter>();
            UsageFactor = new HashSet<UsageFactor>();
        }

        public int messageType300SID { get; set; }

        public int MarketMessageID { get; set; }

        [Required]
        [StringLength(11)]
        public string MPRN { get; set; }

        [StringLength(35)]
        public string MPBR { get; set; }

        [Required]
        [StringLength(35)]
        public string NetworkReferenceNumber { get; set; }

        [Required]
        [StringLength(3)]
        public string LoadProfileCode { get; set; }

        [Required]
        [StringLength(4)]
        public string DUoSGroup { get; set; }

        [Required]
        [StringLength(2)]
        public string MeterPointStatusCode { get; set; }

        public DateTime ReadDate { get; set; }

        public virtual MarketMessage MarketMessage { get; set; }

        [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA2227:CollectionPropertiesShouldBeReadOnly")]
        public virtual ICollection<Meter> Meter { get; set; }

        [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA2227:CollectionPropertiesShouldBeReadOnly")]
        public virtual ICollection<UsageFactor> UsageFactor { get; set; }
    }
}

MODEL LEVEL 3

namespace BillingEngine.DAL
{
    using System;
    using System.Collections.Generic;
    using System.ComponentModel.DataAnnotations;
    using System.ComponentModel.DataAnnotations.Schema;
    using System.Data.Entity.Spatial;

    [Table("Meter")]
    public partial class Meter
    {
        [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA2214:DoNotCallOverridableMethodsInConstructors")]
        public Meter()
        {
            RegisterLevelInformation = new HashSet<RegisterLevelInformation>();
        }

        public int MeterID { get; set; }

        [StringLength(15)]
        public string MeterCategoryCode { get; set; }

        [Required]
        [StringLength(9)]
        public string SerialNumber { get; set; }

        [StringLength(3)]
        public string MeterLocationCode { get; set; }

        public int? MessageType300ID { get; set; }

        public int? MessageType300SID { get; set; }

        public int? MessageType300WID { get; set; }

        public int? MessageType303RID { get; set; }

        public int? MessageType305ID { get; set; }

        public int? MessageType306ID { get; set; }

        public int? MessageType306WID { get; set; }

        public int? MessageType307ID { get; set; }

        public int? MessageType307WID { get; set; }

        public int? MessageType310ID { get; set; }

        public int? MessageType310WID { get; set; }

        public int? MessageType320ID { get; set; }

        public int? MessageType320WID { get; set; }

        public int? MessageType341ID { get; set; }

        public int? MessageType342ID { get; set; }

        public virtual messageType300 messageType300 { get; set; }

        public virtual messageType300S messageType300S { get; set; }

        public virtual messageType300W messageType300W { get; set; }

        public virtual messageType305 messageType305 { get; set; }

        [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA2227:CollectionPropertiesShouldBeReadOnly")]
        public virtual ICollection<RegisterLevelInformation> RegisterLevelInformation { get; set; }
    }
}

MODEL LEVEL 4

namespace BillingEngine.DAL
{
    using System;
    using System.Collections.Generic;
    using System.ComponentModel.DataAnnotations;
    using System.ComponentModel.DataAnnotations.Schema;
    using System.Data.Entity.Spatial;

    [Table("RegisterLevelInformation")]
    public partial class RegisterLevelInformation
    {
        public int RegisterLevelInformationID { get; set; }

        [Required]
        [StringLength(3)]
        public string MeterRegisterSequence { get; set; }

        [Required]
        [StringLength(10)]
        public string TimeslotCode { get; set; }

        [Required]
        [StringLength(3)]
        public string UOM_Code { get; set; }

        public decimal MeterMultiplier { get; set; }

        public decimal ReadingValue { get; set; }

        [Required]
        [StringLength(2)]
        public string ReadReasonCode { get; set; }

        [Required]
        [StringLength(2)]
        public string ReadTypeCode { get; set; }

        public DateTime? PreviousReadDate { get; set; }

        public decimal Consumption { get; set; }

        public decimal EstimatedConsumption { get; set; }

        [StringLength(4)]
        public string ReadStatusCode { get; set; }

        [StringLength(2)]
        public string RegisterTypeCode { get; set; }

        [StringLength(1)]
        public string PostDecimalDetails { get; set; }

        [StringLength(2)]
        public string PreDecimalDetails { get; set; }

        public int? MeterID { get; set; }

        public int? RemovedMeterRegisterID { get; set; }

        public int? NewMeterRegisterID { get; set; }

        public int? RetainedMeterRegisterID { get; set; }

        public virtual Meter Meter { get; set; }
    }
}

Answer 1

Since, no one else is going to answer from the comments, I will.

Try changing this:

<td>
    @foreach (var m in item.messageType300S.Select(m => m.Meter).FirstOrDefault())
    {
        @Html.Display(m.SerialNumber)
    }
</td>

To:

<td>
    @foreach (var m in item.messageType300S.Select(m => m.Meter).FirstOrDefault())
    {
        @Html.DisplayFor(x => m.SerialNumber)
    }
</td>

Html.Display => Returns HTML markup for each property in the object that is represented by a string expression.

Html.DisplayFor => Returns HTML markup for each property in the object that is represented by the System.Linq.Expressions.Expression expression.

UPDATE:

If you are looking into looping through each Meter using ToList() and then displaying details of each meter then can do this:

<td>
    @foreach (var m in item.messageType300S.SelectMany(y => y.Meter).ToList())
    {
        @Html.DisplayFor(y => m.SerialNumber)
        @Html.DisplayFor(y => m.OtherPropertyDetail) 
        @Html.DisplayFor(y => m.AnotherPropertyDetail)
    }
</td>

You are going to have to use SelectMany since Meter is already of type ICollection .. so if you just use Select you will generate something along these lines List<List<Meter>[]> .. so SelectMany will flatten that out to just a List<Meter> which is what you are looking for.