ASP.NET - 如何仅在尚未包含 CSS 时才包含它? [英] ASP.NET - How to include CSS only if it isn't already included?

问题描述

我使用下面的代码来动态包含一个 CSS 文件:

I use the code bellow to dynamically include a CSS file:

HtmlHead head = (HtmlHead)Page.Header;
HtmlLink link = new HtmlLink();
link.Attributes.Add("href", Page.ResolveClientUrl("~/App_Themes/Default/StyleSheet.css"));
link.Attributes.Add("type", "text/css");
link.Attributes.Add("rel", "stylesheet");
head.Controls.Add(link);

问题是:我只想做一次，而且只有当它没有真正包含在页面中时.

The problem is: I want to do it only once, and only if it isn't alrealy included in the page.

我如何验证它是否已经包含在内?

How do I verify if it is already included?

告诉我使用 !IsPostBack 包含在页面加载中的答案不会解决我的问题，因为此代码将位于 Web 用户控件中，并且我的页面可能有很多相同的用户控件.

Answers telling me to include in page load using !IsPostBack won't solve my problem, as this code will be inside a Web User Control and my page may have a lot of the same user control.

例如，我用下面的代码用javascript来做:

For example, I use the code below to do it with javascript:

if (!Page.ClientScript.IsClientScriptIncludeRegistered("jsScript"))
{
    Page.ClientScript.RegisterClientScriptInclude("jsScript", ResolveUrl("~/Utilities/myScript.js"));
}

推荐答案

做到了...

我使用的代码如下:

        Boolean cssAlrealyIncluded = false;
        HtmlLink linkAtual;
        foreach (Control ctrl in Page.Header.Controls)
        {
            if (ctrl.GetType() == typeof(HtmlLink))
            {
                linkAtual = (HtmlLink)ctrl;

                if (linkAtual.Attributes["href"].Contains("datePicker.css"))
                {
                    cssAlrealyIncluded = true;
                }
            }
        }

        if (!cssAlrealyIncluded)
        {
            HtmlLink link = new HtmlLink();
            link.Attributes.Add("href", ResolveUrl("~/Utilities/datePickerRsx/datePicker.css"));
            link.Attributes.Add("type", "text/css");
            link.Attributes.Add("rel", "stylesheet");
            Page.Header.Controls.Add(link);
        }

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