如何在asp.net核心中使用ViewDataDictionary和Html.Partial？

Question

我的情况如下:

模型:

public class Book
{
    public string Id { get; set; }

    public string Name { get; set; }
}

public class Comment
{
    public string Id { get; set; }

    public string BookId { get; set; }

    public string Content { get; set; }    
}

控制器:

public IActionResult Detail(string id)
{
    ViewData["DbContext"] = _context; // DbContext

    var model = ... // book model

    return View(model);
}

视图:

详细视图:

@if (Model?.Count > 0)
{
    var context = (ApplicationDbContext)ViewData["DbContext"];
    IEnumerable<Comment> comments = context.Comments.Where(x => x.BookId == Model.Id);

    @Html.Partial("_Comment", comments)
}

评论局部视图:

@model IEnumerable<Comment>

@if (Model?.Count > 0)
{
    <!-- display comments here... -->
}

<-- How to get "BookId" here if Model is null? -->

我试过这个:

@Html.Partial("_Comment", comments, new ViewDataDictionary { { "BookId", Model.Id } })

然后

@{
    string bookid = ViewData["BookId"]?.ToString() ?? "";
}

@if (Model?.Count() > 0)
{
    <!-- display comments here... -->
}

<div id="@bookid">
    other implements...
</div>

但是错误:

'ViewDataDictionary'不包含带0参数的构造函数

当我选择ViewDataDictionary并按下时F12,它会命中:

namespace Microsoft.AspNetCore.Mvc.ViewFeatures
{
    public ViewDataDictionary(IModelMetadataProvider metadataProvider, ModelStateDictionary modelState);
}

我不知道是什么IModelMetadataProvider和ModelStateDictionary？

我的目标:将模型comments从视图发送Detail.cshtml到部分视图_Comment.cshtml,ViewDataDictionary其中包含BookId.

我的问题:我怎么能这样做？

Answer 1

另一种使用它的方法是ViewData将当前视图传递给构造函数.这样ViewDataDictionary,使用集合初始化程序放入的项目会扩展新的内容.

@Html.Partial("MyPartial", new ViewDataDictionary(ViewData) { { "BookId", Model.Id } })

Answer 2

使用以下代码创建ViewDataDictionary

new ViewDataDictionary(new Microsoft.AspNetCore.Mvc.ModelBinding.EmptyModelMetadataProvider(), new Microsoft.AspNetCore.Mvc.ModelBinding.ModelStateDictionary()) { { "BookId", Model.Id } }

Answer 3

在 .NET Core 上，我使用带有参数的 ViewDataDictionary，例如：

@Html.Partial("YourPartial", new ViewDataDictionary(ViewData) { { "BookId", Model.Id } })