title: knockout validation isvalid method
body: <p>Is it not posssible to use isvalid method inside viewmodel? I got error isvalid in not a valid function. </p>
  
  <pre><code>   function Student(name,age,country) {
              var self = this;
              self.Name = ko.observable(name).extend({ required: true });
              self.Age = ko.observable(age);
              self.Country = ko.observable(country);
          };
          /*----------------------------------------------------------------------*/
          /* View Model
          /*----------------------------------------------------------------------*/
          function StudentViewModel() {
              var self = this;
              self.students = ko.observableArray([]);
              self.countries =ko.observableArray([]);
              this.errors = ko.validation.group(this.students, { deep: true });
              self.editingItem = ko.observable();
              self.isItemEditing = function(itemToTest) {
                  return itemToTest == self.editingItem();
              };
              self.addStudent = function () {
                  var student = new Student("New name","0", self.countries[0]);
                  self.students.push(student);
  
                  //  begin editing the new item straight away
                  self.editStudent(student);
              };
  
              self.removeStudent = function (student) {
                  if (student.Name()) {
                      if (confirm('Are you sure you wish to delete this item?')) {
                          if (self.editingItem() == null) {
                              self.students.remove(student);
                          }
                      }
                  }
  
              };
  
              self.editStudent = function (student) {
                  // if (self.editingItem() == null) {
                  // shows the edit fields
                  self.editingItem(student);
                  // }
              };
  
              self.applyStudent = function (student) {
                  //  hides the edit fields
                  //jQuery("#form1").valid();
                  //alert(self.isValid());
                  alert(self.isValid());
                  if(self.isValid())
                      {
                      self.editingItem(null);
                      }
              };
  
              self.cancelStudent = function (student) {
                  //  hides the edit fields
                  self.editingItem(null);
              };
  </code></pre>