空项为 HTML <option> for abp-select

Question

在 Razor 页面中，您可以通过执行类似于此的操作为 select 指定一个空的第一项：

<select asp-for="SelectedTags" asp-items="Model.TagOptions">
    <option value="">Choose a tag</option>
</select>

是否有 abp-select 标签助手的选项，例如：

<abp-select asp-for="Mentor.RegionId" asp-items="Model.Regions">
    <option value="">Choose a region</option>
</abp-select>

参考：https://docs.microsoft.com/en-us/aspnet/core/mvc/views/working-with-forms?view=aspnetcore-5.0#the-select-tag-helper

Answer 1

从 ABP 4.3.0 开始是不可能的，因为 AbpSelectTagHelperService 修改了 output.Content 而没有调用和使用 output.GetChildContentAsync.

的结果

public override async Task ProcessAsync(TagHelperContext context, TagHelperOutput output)
{
    var innerHtml = await GetFormInputGroupAsHtmlAsync(context, output);

    ...

    if (suppress)
    {
        output.SuppressOutput();
    }
    else
    {
        output.TagName = "div";
        ...
        output.Content.SetHtmlContent(innerHtml);
    }
}

protected virtual async Task<string> GetFormInputGroupAsHtmlAsync(TagHelperContext context, TagHelperOutput output)
{
    var selectTag = await GetSelectTagAsync(context, output);
    ...
}

protected virtual async Task<TagHelperOutput> GetSelectTagAsync(TagHelperContext context, TagHelperOutput output)
{
    ...

    var selectTagHelperOutput = await selectTagHelper.ProcessAndGetOutputAsync(GetInputAttributes(context, output), context, "select", TagMode.StartTagAndEndTag);

    // selectTagHelperOutput.Content.SetHtmlContent(childContent); // Missing
    ...
}

参考文献：

• https://github.com/abpframework/abp/pull/8781
• https://docs.microsoft.com/en-us/aspnet/core/mvc/views/tag-helpers/authoring?view=aspnetcore-5.0#inspect-and-retrieve-child-content