AspNetCore在TagHelper中获取wwwroot的路径

本文关键字：wwwroot 路径 获取 TagHelper AspNetCore | 更新日期: 2023-09-27 18:12:49

我尝试创建一个TagHelper来检查图像是否存在，如果不存在则替换默认图像的路径。

不幸的是，我在标签帮助器中映射"~"符号时遇到了问题。

例如

。我的图像src包含"~'images'image1.png"。现在我想检查这个文件是否存在，如果不存在，就用标签属性中的另一个文件替换它。我被困在映射"~"到我的应用程序的wwwroot。

这是我实际得到的:

[HtmlTargetElement("img", TagStructure = TagStructure.WithoutEndTag)]
public class ImageTagHelper : TagHelper
{
    public ImageTagHelper(IHostingEnvironment environment)
    {
        this._env = environment;
    }
    private IHostingEnvironment _env;
    public string DefaultImageSrc { get; set; }
    public override void Process(TagHelperContext context, TagHelperOutput output)
    {
    //    urlHelper.ActionContext.HttpContext.
    //var env = ViewContext.HttpContext.ApplicationServices.GetService(typeof(IHostingEnvironment)) as IHostingEnvironment;
        string imgPath = context.AllAttributes["src"].Value.ToString();
        if (!File.Exists(_env.WebRootPath + imgPath)) {
            output.Attributes.SetAttribute("src", _env.WebRootPath + DefaultImageSrc);
        }
    }
}

AspNetCore在TagHelper中获取wwwroot的路径

你应该接受IUrlHelperFactor和IActionContextAccessor的构造函数依赖，这将使你能够获得一个IUrlHelper，它可以通过"~/"语法从wwwroot解析url 

public ImageTagHelper(
    IUrlHelperFactory urlHelperFactory,
    IActionContextAccessor actionContextAccesor,)
{
    this.urlHelperFactory = urlHelperFactory;
    this.actionContextAccesor = actionContextAccesor;
}
private IUrlHelperFactory urlHelperFactory;
private IActionContextAccessor actionContextAccesor;
public override void Process(TagHelperContext context, TagHelperOutput output)
{
    var urlHelper = urlHelperFactory.GetUrlHelper(actionContextAccesor.ActionContext);
    var myUrl = urlHelper.Content("~/somefilebelowwwwroot");
    ...
}

可以看到我在PagerTagHelper中做了

需要在Startup.cs

的ConfigureServices方法中添加一个

您需要添加以下行:

        services.AddSingleton<IHttpContextAccessor, HttpContextAccessor>();
        services.AddSingleton<IActionContextAccessor, ActionContextAccessor>();

然后这个就行了:

   [HtmlTargetElement("img", TagStructure = TagStructure.WithoutEndTag)]
    public class ImageTagHelper : TagHelper
    {
        public ImageTagHelper(IUrlHelperFactory urlHelperFactory,
                              IActionContextAccessor actionContextAccessor,
                              IHostingEnvironment environment)
        {
            _urlHelperFactory = urlHelperFactory;
            _actionContextAccessor = actionContextAccessor;
            _env = environment;
        }
        private IUrlHelperFactory _urlHelperFactory;
        private IActionContextAccessor _actionContextAccessor;
        private IHostingEnvironment _env;
        public string DefaultImageSrc { get; set; }
        public override void Process(TagHelperContext context, TagHelperOutput output)
        {
            string imgPath = context.AllAttributes["src"].Value.ToString();
            IUrlHelper urlHelper = _urlHelperFactory.GetUrlHelper(_actionContextAccessor.ActionContext);
            if (!imgPath.StartsWith("data:"))
            {
                if (!File.Exists(_env.WebRootPath + urlHelper.Content(imgPath)))
                {
                    if (DefaultImageSrc != null)
                    {
                        output.Attributes.SetAttribute("src", urlHelper.Content(DefaultImageSrc));
                    }
                }
            }
        }
    }
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