Add to Global.asax.cs and call InitJQuery on Application_Start() to avoid "WebForms UnobtrusiveValidationMode requires a ScriptResourceMapping for 'jquery'" on migrating to ASP.NET 4.5

snippet_for_Global.asax.cs

        private void InitJQuery()
        {
            string jQueryVersion = JQueryInstalledVersion;
            ScriptManager.ScriptResourceMapping.AddDefinition("jquery", new ScriptResourceDefinition {
                Path = "~/Scripts/jquery-" + jQueryVersion + ".min.js",
                DebugPath = "~/Scripts/jquery-" + jQueryVersion + ".js",
                CdnPath = "https://ajax.aspnetcdn.com/ajax/jQuery/jquery-" + jQueryVersion + ".min.js",
                CdnDebugPath = "https://ajax.aspnetcdn.com/ajax/jQuery/jquery-" + jQueryVersion + ".js",
                CdnSupportsSecureConnection = true,
                LoadSuccessExpression = "window.jQuery"
            });
        }

        private string JQueryInstalledVersion
        {
            get
            {
                var scriptsDir = Context.Server.MapPath("~/Scripts/");
                foreach (var file in System.IO.Directory.EnumerateFiles(scriptsDir, "jquery-*.min.js")) {
                    var match = Regex.Match(file, @"(\d+(?:\.\d+){1,3})(\.js)");
                    if (match.Success) {
                        return match.Groups[0].Value;
                    }
                }
                throw new InvalidOperationException("jQuery is not installed in the ~/Scripts dir");
            }
        }

Thanks to Hao Kung, b_levitt

Based on **b_levitt** answer to http://stackoverflow.com/questions/16660900/webforms-unobtrusivevalidationmode-requires-a-scriptresourcemapping-for-jquery
But avoiding hardcoding the jQuery version (doesn't play nice with nuget) by using some regex as explained by **Hao Kung** on http://stackoverflow.com/questions/12029161/version-wildcard-in-mvc4-bundle

If you have jQuery in /Scripts/ but you get the exception you might want to delete '(.js)' in the Regex string.

I included 'min.' in the the Regex.match to
var match = Regex.Match(file, @"(\d+(?:\.\d+){1,3})(\.min.js)");
and it worked better for me.

Thanks @KlausKurzawa, only a nitpick (\.min\.js) instead of (\.min.js)

Thank you for the script, I have used it successfully, just with a minor fix:

The return value of JQueryInstalledVersion property should be: match.Groups[1].Value

match.Groups[0].Value returns version and extension like this: "3.7.1.min.js"