使用asp-for作为参数的自定义ViewComponent

Question

我要包装这个:

<textarea asp-for="@Model.Content" ...>

到可重用的ViewComponent,其中属性将是参数:

<vc:editor asp-for="@Model.Content" />

我能够将asp-for参数传递给viewcomponent:

public class EditorViewComponent : ViewComponent
{
    public IViewComponentResult Invoke(ModelExpression aspFor = null)
    {
        //when debugging, aspFor has correct value
        return View(aspFor);
    }
}

但我无法在组件的视图中评估它.这不起作用:

<!-- ViewComponents/Editor/Default.cshtml -->
@model Microsoft.AspNetCore.Mvc.ViewFeatures.ModelExpression
<textarea asp-for="@Model" />

有任何想法吗？

Answer 1

如果您想将 ModelExpression 传递给底层 ViewComponent，然后将其传递给 TagHelper，则必须使用@TheModelExpression.Model：

<!-- ViewComponents/Editor/Default.cshtml -->
@model Microsoft.AspNetCore.Mvc.ViewFeatures.ModelExpression
<textarea asp-for="@Model.Model" />

正如 @JoelHarkes 提到的，在这种特殊情况下，自定义 taghelper 可能更合适。不管怎样，我仍然可以在 TagHelper 中渲染 PartialView ala 模板：

[HtmlTargetElement("editor", Attributes = "asp-for", TagStructure = TagStructure.WithoutEndTag)]
public class EditorTagHelper : TagHelper
{
    private HtmlHelper _htmlHelper;
    private HtmlEncoder _htmlEncoder;

    public EditorTagHelper(IHtmlHelper htmlHelper, HtmlEncoder htmlEncoder)
    {
        _htmlHelper = htmlHelper as HtmlHelper;
        _htmlEncoder = htmlEncoder;
    }

    [HtmlAttributeName("asp-for")]
    public ModelExpression For { get; set; }

    [ViewContext]
    public ViewContext ViewContext
    {
        set => _htmlHelper.Contextualize(value);
    }


    public override async Task ProcessAsync(TagHelperContext context, TagHelperOutput output)
    {
        output.TagName = null;

        var partialView = await _htmlHelper.PartialAsync("TagHelpers/Editor", For);

        var writer = new StringWriter();
        partialView.WriteTo(writer, _htmlEncoder);

        output.Content.SetHtmlContent(writer.ToString());
    }
}

.cshtml 模板将看起来与视图组件中的一模一样。