Category: HowTo

short tutorials

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 Winking smile

 

 

Prerequisites:

  1. 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/.
  2. 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.
  3. 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


Display:

clip_image002

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.

clip_image004

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:

clip_image006

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:

  1. obj is the object in javascript that I need all properties that are number, string, or boolean.
  2. 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;
    
    }
    
    
  3. 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

clip_image008

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/#!

MVC Export List of objects to Excel-Word-PDF-CSV-HTML-XML–Razor style

This is the second part of the demo of the Exporter  in action  – this time in MVC .

It is a little more complicated, because you need to show to the exporter the full path where to put the generated file

string filePathExport = Server.MapPath(“~/exports/a” + ExportBase.GetFileExtension((ExportToFormat)id));

All others are the same easy stuff  -add Nuget package and export in 3 lines – and all action code is 6 lines long:

            List<Electronics> list = Electronics.GetData();
            ExportList<Electronics> exp = new ExportList<Electronics>();
            exp.PathTemplateFolder = Server.MapPath("~/ExportTemplates/electronics");
            string filePathExport = Server.MapPath("~/exports/a" + ExportBase.GetFileExtension((ExportToFormat)id));
            exp.ExportTo(list, (ExportToFormat)id, filePathExport);
            return this.File(filePathExport, "application/octet-stream", System.IO.Path.GetFileName(filePathExport));

 

 

 

 

GitHub Demo at https://github.com/ignatandrei/Export_Word_Excel_PDF_CSV_HTML

The Nuget package is at http://www.nuget.org/packages/Exporter/

YouTube demo at http://youtu.be/DHNRV9hzG_Y

SameId – skip

In the previous post I have show how two users can see each other if they are editing the same product ( in my example , product id 5)

But not in all cases the users should be notified about each other – like in , let’s say, view product Id 5.

In this case we have an attribute to apply to the action [SameIdSkip]

A video will show you :

Same object edited by 2 users–proactively notifying users

This is a practical example about how two users that comes on the same page will be notified one about other( after an idea of Adrian Petcu) . See the picture :

image

With the NuGet package you can install in your application in this steps:

To run :
1. install package from Nuget
2. in Filter.Config add following line:  filters.Add(new SameIdAlert.SameIdFilter());
3. In Route.Config, after
routes.MapHubs();
GlobalHost.DependencyResolver.Register(typeof(IAssemblyLocator) ,() => new SameIdAlert.SameIdAssemblyLocator());
4. In the View that you want the user to be notified add the following lines in the @section scripts{
<!–Script references. –>
<!–The jQuery library is required and is referenced by default in _Layout.cshtml. –>
<!–Reference the SignalR library. –>
<script src=”~/Scripts/jquery.signalR-1.1.3.js”></script>  <!–or whatever signalr library version you have –>
<!–Reference the autogenerated SignalR hub script. –>
<script src=”~/signalr/hubs”></script>
<!–SignalR script to update the chat page and send messages.–>

and somewhere:

@{Html.RenderPartial(“SameId”);}

5. In _Layout  move jquery declaration
@Scripts.Render(“~/bundles/jquery”)

before RenderBody

6. If you decide to put into _Layout and you want to skip an action, please put  [SameIdSkipAttribute] to the action

7. If you want more action parameters than the default id , just put
[SameIdAttribute(“parameter name 1″,”parameter name2”)
to the action
8. If you decide that you want just several actions then modify
filters.Add(new SameIdAlert.SameIdFilter(false));
and put
[SameIdAttribute]
View online at http://SameId.apphb.com

Source code at https://github.com/ignatandrei/SameId

NuGet package at https://www.nuget.org/packages/sameid

Video demo at http://youtu.be/wjkoMs98Z8U

If you want to help me, see the issues that can be solved here:https://github.com/ignatandrei/SameId/issues

MVC Help View Razor

My passion for .tt files is great . T4MVC is the best example of what you can achieve with .tt files in MVC . 

Now, the problem: For each project you have a help file must be created. I mostly work with ASP.NET MVC projects – so I frequently have this problem.

I have then created a .tt file that generates summary help .cshtml Razor files for each View that you have in an ASP.NET MVC project.  This .t t file generates for you the folder structure (including Areas ) for having a view help file for each view that you have in the project.
More, if the help file already exists in the project, it will be not overwritten.

The template can be customized:
-the folder name:
//change here the location folder where the help files will be generated
static string HelperFolderName="Help";
-the content of the file
//change here the default content of the file
string TextFile = "<html><body>This is the help file for the view {0}</body></html>";

(For improvements please create an issue on github)
See demo at http://youtu.be/ZGsNHyFA9yw
You can download from https://github.com/ignatandrei/RazorHelpFile/ 

Use the help file with

<a href=’@Url.Content("~/Help/Views/Home/Index.cshtml")’ target="_blank">Index Help</a>

Enjoy!

MVC , JsonResult , DateTime and TimeZone

The jsonresult of date time is serializing to the string /Date and some integer value starting with 1970 . The problem is that the browser interprets this value accordingly to the LOCAL TimeZone – and thus the same date is going to be interpreted with a difference.

I was thinking that I can adjust from UTC time offset of the server( obtained with .NET from TimeZoneInfo.Local.BaseUtcOffset.TotalMinutes) and the UTC time offset of the client( obtained with (new Date()).getTimezoneOffset() + UTCServerMinutes; ). Unfortunately, the code does not work for SAMOA ( 13 hours difference).

Pay attention that the server is sending SAME data – just the browser is interpreting from the local user time zone.

So the solution is to convert the  date to a string ( I have chosed yyyy-MM-ddTHH:mm:ss) and interpret in javascript( see date2 below).

The server code – I have put my birthdate 16 april 1970

DateTime res = new DateTime(1970, 04, 16, 22, 0, 0);
[HttpPost]
        public JsonResult GetDateBirth()
        {

            var str = res.ToString("s");
            return Json(new { date =res, datestring=str, ok = true });

        }

The Javascript code:

function GetJsonDate() {
        $.ajax({
            type: "POST",
            url: '@Url.Action("GetDateBirth")',
            datatype: "JSON",
            contentType: "application/json; charset=utf-8",
            success: function (returndata) {
                if (returndata.ok) {
                    window.alert('The server is sending:' + returndata.date + " -- " + returndata.datestring);
                    var d = parseInt(returndata.date.substr(6));
                    var date1 = new Date(d);
                    var date2 = dateFromSortable(returndata.datestring);
                    var date3= getDateString(returndata.date);
                    window.alert('original: ' + date1  + '\r\n'  + ' iso correct:'+ date2 + '\r\n'+ ' utc difference not good:' + date3);

                }
                else {
                    //this is an error from the server
                    window.alert(' error : ' + returndata.message);
                }

            }
        }
        );
    }
    function dateFromSortable(dateStr) {
        var parts = dateStr.match(/\d+/g);
        return new Date(parts[0], parts[1] - 1, parts[2], parts[3], parts[4], parts[5]);
    }
    
    function getDateString(jsonDate) {
        //does not work correctly for SAMOA - it have some hours difference
        var UTCServerMinutes = @serverMinutes;
        if (jsonDate == undefined) {
            return "";
        }
        var utcTime = parseInt(jsonDate.substr(6));

        var dateUtc = new Date(utcTime);

        var minutesOffset = (new Date()).getTimezoneOffset() + UTCServerMinutes;

        var milliseconds = minutesOffset * 60000;
        var d = new Date(dateUtc.getTime() + milliseconds)
        return d;
    }

How to test it:

Run the project. Click “Get Json Date” – and you will see the three dates equal.

image

Now change the time zone to Samoa ( or other, if you live in Samoa Winking smile)

image

Click again on “Get Json Date”  – the date will  same 16 april 1970 just for the date2  – obtained from dateFromSortable javascript function.

image

Please note that the local time zone is NOT affecting the values transmitted via ViewBag/ViewData/Model, but just the ones transmitted via Json.

The project can be downloaded from here

MVC and auto persisting values

When you have a textbox in HTML (let’s say

<input name=”FirstName” type=”text” />

)
And it binds to “FirstName” Property of a Model, and in HttpPost Action you do modify the value and return the same view, the value shown in the textbox is the posted one, not the modified one. ( The first thought is that HttpPost is not executing – but it is a false impression!)
The solution is:
ModelState.Remove(“FirstName”)

or, better

http://lennybacon.com/2010/09/07/RemovingPropertiesFromTheModelStateTheTypedWay

(and it’s not a bug, it’s a feature: classical example: numeric textbox/ numeric property and user enters “aaa” – the validation error appears and the textbox must have aaa, not 0 or default value for the property )

Redirect and Ajax Redirect in MVC

In the sample example I will have various methods to perform redirects from main page to “About” page of a simple MVC site. In my opinion, there are only 3 cases – 2 goods and one bad – to perform redirection with or without Ajax.

 

First case:  A sample redirect and a sample link:

The action is

 public ActionResult RedirectToAboutNoAjax()
        {
            return RedirectToAction("About");
        }

and in the View I call in a simple <a href, generated by :

@Html.ActionLink("Redirect no ajax to about", "RedirectToAboutNoAjax", "Home")

When you click the link, the following happens : a 302 Found answer is send to the browser with the new Location. The browser goes to the page requested.
image
  

Second case( not good ajax): Call same action from ajax – in hope that ajax will do the redirect alone, without coding further.Modified only the code that calls the action, transforming to ajax.

<a href="javascript:AjaxNotGoodForRedirect('@Url.Action("RedirectToAboutNoAjax", "Home")')">Redirect not good with ajax - returns the page</a>

 What it happens is the same: the ajax code calls the RedirectToAboutNoAjax , that redirects to about – and the result is the page. It is no redirect performed to the page itself – rather, on the ajax itself!And , to proof it, I will show the message of html returned in an message:image

Third case( good with ajax): Call a action that returns the new url as a json data parameter and make javascript know that.The action:

 [HttpPost]
        public ActionResult RedirectToAboutWithAjax()
        {
            try
            {
                
                //in a real world, here will be multiple database calls - or others
                return Json(new { ok = true, newurl = Url.Action("About") });
            }
            catch (Exception ex)
            {
                //TODO: log
                return Json(new { ok = false, message = ex.Message });
            }
        }

The javascript:

function AjaxGoodRedirect(urlAction) {
        $.ajax({
            type: "POST", // see http://haacked.com/archive/2009/06/24/json-hijacking.aspx
            url: urlAction,
            data: {}, //to send data see more at http://bit.ly/mvc_ajax_jquery
            datatype: "JSON",
            contentType: "application/json; charset=utf-8",
            success: function (returndata) {
                if (returndata.ok)
                    window.location = returndata.newurl;
                else
                    window.alert(returndata.message);

            }
        }
        );
    }

Note: You can combine the returning the RedirectToAction with Json by checking Request.IsAjaxRequest value and returning either FirstCase, either ThirdCase.

You can find the example for download here
If you want more details, please comment – and I will provide any further explanations.