//$.validator.addMethod("NoSpecialChars", function (value, element) {
//    return this.optional(element) || /^[a-z 0-9åæøÅÆØÄäöÖ\_\-]+$/i.test(value);
//}, "Username must contain only letters, numbers, or underscore.");

$.validator.addMethod("NoSpecialChars", function (value, element) {
    return this.optional(element) || /^[a-z A-Z0-9ÁÀÂÃÄÆÇÈÉÊËÌÍÎÐÏÑÒÓÔÕÖØÙÚßàáâãäåæçèéêëìíîïðñòóôõöøùúûüýþÞÿÛÜ\_\-\.]+$/i.test(value);
}, "Username must contain only letters, numbers, or underscore.");