private static System.Web.Optimization.Bundle DoIncludeFallback(this System.Web.Optimization.Bundle bundle, string fallback,
string className = null, string ruleName = null, string ruleValue = null)
{
if (!(bundle is StyleBundle) && (bundle is System.Web.Optimization.StyleBundle))
{
throw new ArgumentException("Not allowed type", nameof(bundle));
}
if (String.IsNullOrEmpty(bundle.CdnPath))
{
throw new ArgumentException("CdnPath must be provided when specifying a fallback", nameof(fallback));
}
if (VirtualPathUtility.IsAppRelative(bundle.CdnPath))
{
bundle.DoCdnFallbackExpress(fallback);
}
else if (new[] { className, ruleName, ruleValue }.Any(String.IsNullOrEmpty))
{
throw new Exception(
"IncludeFallback for cross-domain CdnPath must provide values for parameters [className, ruleName, ruleValue].");
}
else
{
bundle.DoCdnFallbackExpress(fallback, className, ruleName, ruleValue);
}
return(bundle);
}
private static System.Web.Optimization.Bundle DoCdnFallbackExpress(this System.Web.Optimization.Bundle bundle, string fallback,
string className = null, string ruleName = null, string ruleValue = null)
{
bundle.Include(fallback);
fallback = VirtualPathUtility.ToAbsolute(fallback);
bundle.CdnFallbackExpression = String.IsNullOrEmpty(className)
? String.Format(@"function() {{
var len = document.styleSheets.length;
for (var i = 0; i < len; i++) {{
var sheet = document.styleSheets[i];
if (sheet.href && sheet.href.indexOf('{0}') !== -1) {{
var rules = sheet.rules || sheet.cssRules;
if (rules.length <= 0) {{
document.write('<link href=""{1}"" rel=""stylesheet"" type=""text/css"" />');
}}
}}
}}
return true;
}}()", bundle.CdnPath, fallback)
: String.Format(@"function() {{
var loadFallback,
len = document.styleSheets.length;
for (var i = 0; i < len; i++) {{
var sheet = document.styleSheets[i];
if (sheet.href && sheet.href.indexOf('{0}') !== -1) {{
var meta = document.createElement('meta');
meta.className = '{2}';
document.head.appendChild(meta);
var value = window.getComputedStyle(meta).getPropertyValue('{3}');
document.head.removeChild(meta);
if (value !== '{4}') {{
document.write('<link href=""{1}"" rel=""stylesheet"" type=""text/css"" />');
}}
}}
}}
return true;
}}()", bundle.CdnPath, fallback, className, ruleName, ruleValue);
return(bundle);
}
