detect browser in asp.net using c#

 System.Web.HttpBrowserCapabilities browser = Request.Browser;
        string s = "Browser Capabilities\n"
            + "Type = " + browser.Type + "\n"
            + "Name = " + browser.Browser + "\n"
            + "Version = " + browser.Version + "\n"
            + "Major Version = " + browser.MajorVersion + "\n"
            + "Minor Version = " + browser.MinorVersion + "\n"
            + "Platform = " + browser.Platform + "\n"
            + "Is Beta = " + browser.Beta + "\n"
            + "Is Crawler = " + browser.Crawler + "\n"
            + "Is AOL = " + browser.AOL + "\n"
            + "Is Win16 = " + browser.Win16 + "\n"
            + "Is Win32 = " + browser.Win32 + "\n"
            + "Supports Frames = " + browser.Frames + "\n"
            + "Supports Tables = " + browser.Tables + "\n"
            + "Supports Cookies = " + browser.Cookies + "\n"
            + "Supports VBScript = " + browser.VBScript + "\n"
            + "Supports JavaScript = " +
                browser.EcmaScriptVersion.ToString() + "\n"
            + "Supports Java Applets = " + browser.JavaApplets + "\n"
            + "Supports ActiveX Controls = " + browser.ActiveXControls
                  + "\n"
            + "Supports JavaScript Version = " +
                browser["JavaScriptVersion"] + "\n";

How can I use xsl:value-of in image path

<img>

<xsl:attribute name="src>/folder/images/<xsl:value-of select="thumbnail"/></xsl:attribute>

</img>

2

<img><xsl:attribute name="src">/folder/images/<xsl:value-of select='thumbnail' /></xsl:attribute></img>