从其他模型的剃刀视图编辑参考模型的值

Question

This is my first time using MVC in a business capacity, so please forgive me if this is an easily answered question.

My issue is that I have a razor view for editing a model, we will call it MainModel . Here is a reduced version of MainModel:

using System;
using System.Collections.Generic;

namespace MyProject.Models
{
public partial class MainModel
{
    public MainModel()
    {
        SecondModel = new HashSet<SecondModel>();
    }

    public int MainModelId { get; set; }
    public DateTime? DueDate { get; set; }
    public int? CreatedByUserId { get; set; }
    public DateTime? CreatedDateTime { get; set; }
    public bool IsActive { get; set; }

    public virtual ICollection<SecondModel> SecondModel { get; set; }
    public virtual Users CreatedByUser { get; set; }
}
}

MainModel has a reference to another Model, SecondModel (original names, I know). This reference is a collection so that it can be looped through with a foreach within the razor view. Here is SecondModel:

namespace MyProject.Models
{
public partial class SecondModel
{
    public int SecondModelId { get; set; }
    public string Comment { get; set; }
    public double? Value { get; set; }
    public int? ThirdModelId { get; set; }
    public bool IsActive { get; set; }

    public virtual ThirdModel ThirdModelVariable { get; set; }
}
}

So my issue is that I need to be able to edit the values of variables such as Comment and Value within SecondModel, but from the razor edit page that is using the model from MainModel.

I've tried a few different variation of this, with no luck.

<input asp-for="SecondModel.Comment" class="form-control" />

Usually trying something like this presents the following error:

ICollection<SecondModel> does not contain a definition for 'Comment' and no extension method 'Comment' accepting a first argument of type 'ICollection<SecondModel>' could be found

You may have noticed that there is also a reference to a ThirdModel within SecondModel. I also need to be able to reference some variables from that model within this view, but I assume the solution for one will be the solution for both in this case. Hopefully I explained that well enough, please let me know if you need to see anymore code to reference or if I wasn't clear enough.

Thanks for your time!

Answer 1

When you specify to what input should be bound, you must specify valid C# accessor (behind the scene this is interpreted as lambda expression which represents access to specific property/field). Error message is telling you that ICollection<SecondModel> does not have property Comment , which is correct since SecondModel property is of type ICollection<SecondModel> and not SecondModel .

To fix your error, you have to retrieve specific element from collection first. So you can either loop the collection and generate input for every element or access specific element if you know it is there. For accessing element you have a problem with your collection type since you cannot use indexer. You should change it to IList<SecondModel> . Then you can for example access write input for comment field for first element in collection like this:

<input asp-for="SecondModel[0].Comment" class="form-control" />

And for accessing ThirdModel :

<input asp-for="SecondModel[0].ThirdModel.SomeProperty" class="form-control" />

I suggest reading Model binding to a list . It is quite old post which does not use tag helpers, but behavior is the same.

Answer 2

ICollection<SecondModel> does not contain a definition for 'Comment'`

The error is clear. You're looking for Comment property in a collection. It should be

@for (int i=0; i< Model.SecondModel.Count(); i++)
{
    <input asp-for="SecondModel[i].Comment" class="form-control" />
    // other properties
}

or use the HTML Helpers :

@for (int i=0; i< Model.SecondModel.Count(); i++)
{
    @Html.TextBoxFor(m => m.SecondModel[i].Comment, new { @class = "form-control" })
     // other properties

    @Html.TextBoxFor(m => m.SecondModel[i].ThirdModelVariable.Property, new { @class = "form-control" })

}

For the indexers to work, you'd have to change the property from an ICollection<SecondModel> to IList<SecondModel>

To avoid this kind of confusion, whenever you have a IList<T> type property, it's better to name them as plurals. In your case:

public virtual IList<SecondModel> SecondModels { get; set; }

Now you'll know you're referring to the SecondModels property rather than keeping it SecondModel and forgetting it's a collection.