ASP.NET-仅在尚未包含CSS的情况下才包含CSS? [英] ASP.NET - How to include CSS only if it isn't already included?

问题描述

我使用下面的代码动态包含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:我只想执行一次，并且只在页面中没有包含它.

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

如何验证它是否已包含?

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无法解决我的问题，因为此代码将位于Web用户控件内，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，我使用下面的代码来使用javascript:

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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