Javascript MVVM and ASP.NET MVC
TL;DR;
The purpose of this article is to show is how to transmit data to edit( create, update, delete) from a MVVM array to an ASP.NET MVC action in order for the action to bind to an IEnumerable/Array/List of objects. We will make also a javascript function that can be re-use across multiple MVVM frameworks to transmit data for multiple objects at once.
As always, you can find source code at https://github.com/ignatandrei/JavaScriptAndMVVMandMVC/ and you can view online at http://mvvmjavascriptmvc.apphb.com/
If you know already that, the last item on this rather long post is a homework. Download code and do it 
Prerequisites:
- If you want to know about ajax, please see the same example of how to save employee one by one http://msprogrammer.serviciipeweb.ro/2011/12/05/jquery-ajax-request-and-mvcdetailed/.
- The reference of sending an array of objects to MVC is http://haacked.com/archive/2008/10/23/model-binding-to-a-list.aspx/ . Please read it first since we will compose the Http request in ASP.NET MVC manner.
- If you do not know about MVVM and data binding in javascript, please follow most comprehensive tutorial that I know, http://learn.knockoutjs.com/
Objects
We start with the Employee ( Id, Name and IdDepartment) and Department(Id, Name). We will make an interface to display and edit multiple employees. The user can choose to change the Name and pick a Department from a list of Departments (presented as a select / dropdown / combox) .Also, he can create new Employee or delete an existing Employee. Then the user can submit all changes at once. We will use for this MVVM from Knockout, but you can use any other MVVM framework.
We will have 2 modes: edit and display. For edit, we have as actions add, delete ,modify and send all modifications(along with validation) . I would list what it is mandatory for every mode and action.
For fast learners:
Display
Edit Mode –Modify existing data
Edit Mode –add new employee
Edit Mode –delete existing employee
Edit Mode –send modifications and client validation
Summary
Homework
As you see we need to display the Employee list with name and the Department name.
If I do not want to create a NameDepartment property on Employee, but just use DepartmentId then the Model of the View should return the list of names of Departments.
public class ListEmployeesViewModel
{
public employeeList AllEmployees { get; set; }
public departmentList DepartmentList{ get; private set; }
This will be serialized as javascript array in the Home view:
@{
var jss = new JavaScriptSerializer();
var arrDepartments = jss.Serialize(Model.DepartmentList);
var arrEmployees = jss.Serialize(Model.AllEmployees);
}
//This is in the script tag in javascript: //existing departments var arrDeps = @Html.Raw(arrDepartments) ; //existing employees var arrEmps = @Html.Raw(arrEmployees) ;
So we have in arrDeps the departments and in arrEmps the existing employees.
To display the list of employees we create a MVVM javascript model( we have here knockout style, but is similar with other javascript MVVM framework)
First we create an employee in javascript ( explanations will follow) :
//this is in javascript
var emp = function(empId,name,deptId,active){
var self = this;
self.nr = i++;
self.IdEmployee = ko.observable(empId);
self.NameEmployee = ko.observable(name);
self.Active = ko.observable(active);
self.iddepartament = ko.observable(deptId);
self.editMode = ko.observable(false);
self.displayMode= ko.observable(true);
self.deptName= function(){
var id=self.iddepartament();
var name ="";
$.each(arrDeps,function(index,value){
if(value.IdDepartment == id){
name=value.NameDepartment;
return false;
}
});
return name;
}
}
Explanation 1: the nr is the number of the employee . The user does not like ID, but wants to know how much employees are displayed.
Explanation 2: I have add an editMode and displayMode to the employee – to know the mode in which the employee is. I can have one property instead of 2(because of complementarity) , but was easier for me.
Explanation 3: In order to display DepartmentName it is enough to create a function on the employee to return the department name , iterating through the arrDeps – the code is
self.deptName= function(){
var id=self.iddepartament();
var name ="";
$.each(arrDeps,function(index,value){
if(value.IdDepartment == id){
name=value.NameDepartment;
return false;
}
});
return name;
}
Now we create the javascript model that holds all employees on the view:
var jsModel = function() {
var self = this;
self.employees = ko.observableArray([]);
And we make a function to add the existing employees to the array of employees:
self.addEmp = function(empId,name,deptId,active) {
self.employees.push(new emp(empId,name,deptId,active))
};
And we add to the javascript MVVM model the existing employees
var model= new jsModel();
$.each(arrEmps,function(index,value){
model.addEmp(value.IdEmployee ,value.NameEmployee, value.iddepartament,value.Active);
});
And display it on the template by just binding :
ko.applyBindings(model);
that will repeat in
<tbody data-bind=’foreach: employees’>
<tr>
<td>
<span data-bind=’text: nr’ > </span>
</td>
<td>
<span data-bind=’text: NameEmployee,visible:displayMode’> </span>
<!—code removed for clarity–>
</td>
<td>
<span data-bind=’text: deptName(),visible:displayMode’> </span>
<!—code removed for clarity–>
</td>
<td>
<span data-bind=’text: Active,visible:displayMode’> </span>
<!—code removed for clarity–>
</td>
<td><!—code removed for clarity–>
</td>
</tr>
So this was the display mode. Pretty simple, huh ?
Edit Mode –Modify existing data
The Edit button calls the javascript model edit(true):
self.edit = function(val){
var arr =self.employees();
$.each(arr ,function(index,value){
value.editMode(val);
value.displayMode(!val);
});
So I put editMode to true and displayMode to false
Now, back to the template:
<td>
<span data-bind=’text: NameEmployee,visible:displayMode’> </span>
<input data-bind=’value: NameEmployee,visible:editMode’ />
</td>
You can see here visible attribute binded on displayModel and editMode –and how the span or the input are visible either way.
Same for the checkbox and the select. Because of the MVVM (in this case, knockout) any changes on the data ( name, active, changing department) will be binded back to the array of employees in the javascript MVVM model
Edit Mode –add new employee
When you press add a new employee is generated – the number 3:
It is easy – the Add button calls the same function addEmp that we use to push existing employees:
function BeginAdd(){
model.addEmp(0,'',0,true);
model.edit(true);
}
So a new employee is added to the array of employees – and the employees table is displaying the added employee . Do you like MVVM now ? 😉
Edit Mode –delete existing employee
The delete button have this code:
<td><button data-bind="click: $root.removeEmp,visible:editMode">Delete</button></td>
It is clear visible just when editMode is true. And the removeEmp removes the current employee from array, but having the id ( if not 0 – means new) put into a string that contains the ids of deletedEmployeesa:
self.removeEmp = function(emp) {
var id=emp.IdEmployee();
if(id != 0)
self.deletedItemsId += id;
self.employees.remove(emp);
};
And the employees table is removing the row for the employee . Do you like MVVM now ? 😉
Edit Mode –send modifications and client validation
On the server side, the parameters of the action that receives the data is simple:
[HttpPost]
[HttpPost] public JsonResult SaveEmployees(ListEmployeesViewModel e,string deletedItems)
I will explain the 2 arguments. For the first, remember ListEmployeesViewModel from the beginning ? It contains the list of employees and we will post that:
public class ListEmployeesViewModel
{
public employeeList AllEmployees { get; set; }
The second argument is the string that contains the id’s of deletedEmployees.
Now to transmit those from javascript array of employees.
Being a programmer, I like code-reuse. So why not create a function that iterates through an array( of employees), get all properties ( eliminating non-relevant, such as nr, editMode, displayModel and others) and compose the data in the MVC style(http://haacked.com/archive/2008/10/23/model-binding-to-a-list.aspx/ )
First, we need reflection in javascript:
//this is generic and can be put in a different .js file
var refProps= function (obj, exclude , recognizeFunction) {
var properties = [];
for (var prop in obj) {
//you can define an exclude function to exclude added properties
if(exclude){
if(exclude(prop))
continue;
}
var excludeProp = true;
var t = (typeof obj[prop]).toLowerCase();
if (t == 'number' || t == 'string' || t == 'boolean') {
excludeProp=false;
}
if(excludeProp){
//special case :maybe it is a observable function
if(recognizeFunction){
if(t == 'function' ){
if(recognizeFunction(t))
excludeProp=false;
}
};
}
if(!excludeProp)
properties.push(prop);
};
return properties;
}
Fast explanation of parameters:
- obj is the object in javascript that I need all properties that are number, string, or boolean.
- I need to remove some properties(nr,editMode, displayMode) that are relevant in javascript – but not on the server side – so I have put an exclude function( you can put null)
function exclude(prop){ switch(prop){ case "nr": return true; case "deptName": return true; case "editMode": return true; case "displayMode": return true; default: return false; } - Also, knockout make a special ko.observable function
self.NameEmployee = ko.observable(name);
– so I need to recognize those functions – and the function is(surprise!) ko.observable
Now saving the array is again re-usable:
function saveArray(itemsArray,/*you can not pass those*/prefix, excludeProp,recognizeFunction,validateProp){
var l = itemsArray.length ;
if(l == 0){
return "";
}
var propNames = refProps(itemsArray[0],excludeProp,recognizeFunction); // you can pass null on exclude to add all properties
var nr = 0 ;
var strData="";
for (var i = 0; i < l; i++) {
var objToSave= itemsArray[i];
//you can pass here another function to recognize which object can be saved
//if(!canBeSaved(objSave) continue;
for (var j = 0; j < propNames.length; j++) {
var nameProp = propNames[j];
var val =objToSave[nameProp] ;
var t = (typeof val).toLowerCase();
if(t == 'function'){
val = objToSave[nameProp]();
}
if (validateProp) {
if (!validateProp(nameProp,val, objToSave, i)) {
return "";
}
}
strData += "&"+ prefix+"[" + nr + "]." + nameProp;
strData += "=" + val;
}
nr++;
}
return strData;
}
The itemsArray parameter is the items array that you want to save ( in my case, the employees).
The new function is validateProp – you can pass null – but this is an implementation that take into consideration that the employee should not have the name empty and the user must select something from the department list:
function validateProperty(propName, value, item, number){
switch(propName){
case "NameEmployee":
if(value == ""){
window.alert("please enter employee name for row number " + (number+1) );
return false;
}
return true;
case "iddepartament":
if(value === undefined || value == 0){
window.alert("please select a department for row number " + (number+1) );
return false;
}
return true;
default:
return true;
}
}
After those 2 re-usable functions( saveArray and refProps ) the code for save is pretty simple:
We obtain the values for employees using saveArray
self.save = function() {
var itemsArray = self.employees();
var strData = saveArray(itemsArray,"AllEmployees",exclude, ko.observable,validateProperty);
if(strData == "")
{
//window.alert("no save");
return;
}
strData="deletedItems=" +self.deletedItemsId + strData;
window.alert("saving:" + strData);
and post to the server.
$.ajax({
type:"POST",
url:'@Url.Content("~/Home/SaveEmployees")' ,
data: strData ,
datatype:"JSON",
//Just we must be attentive: if success , then the id of the new employees( those with id’s 0) must be replaced by the id’s of the id’s generated on server.
//How I identify if multiple new employees? Well, it is easier to delete all employees with id’s 0 and add the id’s that are not already in the array:
var dels=[];
//delete the new items and add the new ones
var idExisting=';';
$.each(self.employees(), function(index,emp) {
if(emp.IdEmployee() == 0 )
dels.push(emp);
else
idExisting += emp.IdEmployee()+";";
});
$.each(dels,function(index,emp) {
self.removeEmp(emp);
});
//add new one
window.alert('add new ones');
$.each(returndata.emps,function(index,emp) {
var id=emp.IdEmployee;
if(idExisting.indexOf(";" + id+";") == -1){// not found - means it is a new one
self.addEmp(emp.IdEmployee ,emp.NameEmployee, emp.iddepartament,emp.Active);
}
});
Also, for Antiforgery token I have used this code
//added antiforgery token
var aft= $('input[name="__RequestVerificationToken"]');
if(aft.length){
strData +="&__RequestVerificationToken=" + aft.val();
}
Well, that was it !
Summary:
We have had an javascript array of employees to edit and send data at once . We have make the POST as for ASP.NET MVC rules. You can re-use the refProps javascript function( that gives you the name of the properties of an object – in our case, employee) and saveArray javascript function – that serialize an javascript array to a recognizable ASP.NET MVC idiom
As always, you can find source code at https://github.com/ignatandrei/JavaScriptAndMVVMandMVC/ and you can view online at http://mvvmjavascriptmvc.apphb.com/
Homework for you:
( fork on github and send me the solution via github)
1. Modify the nr ( the employee order number) such as , when deleting or adding a new employee, the numbers are in good order – not 1 and 3 like in the picture
2. Add a hiredate to the employee . Ensure you transmit the date(Hint: Modify the refProps )
LaterEdit:
Hintea Dan Alexandru made a simple application to show me that a simple json.stringify it is enough for MVC to do this magic.
More , it shows directly in the MVVM model a toDTO that is simplier to use( however, the validation part remains to do)
Source code at https://github.com/hinteadan/MvcAjaxSample/#!
Thanks for the article, this is helpful. Do you have an example pattern of a bulk edit scenario where you can copy and paste rows and columns of data from Excel into a grid for bulk edit?
No. But it a simple send data and parsing .