Dynamically adding a CSS file from an ASP.NET Server Control

I have a custom control and I want to dynamically insert a link to a stylesheet.

Might not be the best solution of the year but it needs to be done. Any idea how to do it?

Everytime I try, Page.Header is null.

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Answers:

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Method 1

Here’s how you would normally add a CSS programatically:

protected void Page_Init(object sender, EventArgs e)
{
    var link = new HtmlLink();
    link.Href = "~/styles/main.css";
    link.Attributes.Add("rel", "stylesheet");
    link.Attributes.Add("type", "text/css");
    Page.Header.Controls.Add(link);
}

You might need to put a runat="server" in the head tag:

<head runat="server">
    <title>Add CSS example</title>
</head>

Method 2

To avoid the problem of multiple stylesheets when adding the control 10 times to the page, change the above code slightly:

string styleSheet = "stylesheetName.css";
if (this.Page.Header.FindControl(styleSheet) == null)
{
    HtmlLink cssLink = new HtmlLink();
    cssLink.ID = styleSheet;
    cssLink.Href = "~/styles/" + styleSheet;
    cssLink.Attributes.Add("rel", "stylesheet");
    cssLink.Attributes.Add("type", "text/css");
    this.Page.Header.Controls.Add(cssLink);
}

By giving the control an ID you can check if it already exists, and so ensure that you only add it the once.

All methods was sourced from stackoverflow.com or stackexchange.com, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0

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