cors for rest web api

to add support for CORS

  1. install package
    Install-Package Microsoft.AspNet.WebApi.Cors
  2. add to WebApiConfig.Register method
  3. To enable CORS for all Web API controllers in your application, pass an EnableCorsAttribute instance to the EnableCors method:
     var cors = new EnableCorsAttribute("", "*", "*");

In the case you have token oauth authentication for rest web api, fix the pre-flight request cors issue:

  1. Move the code to the first line Startupapp.UseCors(Microsoft.Owin.Cors.CorsOptions.AllowAll);
  2. REMOVE  context.OwinContext.Response.Headers.Add("Access-Control-Allow-Origin", new[] { "*" }); from the GrantResourceOwnerCredentials()





VS 2015 Package Manager Console Failed

Opening package manager console produce the error message:

“Windows PowerShell updated your execution policy successfully, but the setting is overridden by a policy defined at a more specific scope. Due to the override, your shell will retain its current effective execution policy of Unrestricted. Type “Get-ExecutionPolicy -List” to view your execution policy settings. For more information please see “Get-Help Set-ExecutionPolicy”.”

A temp fix is update the regedit

"ExecutionPolicy" set to empty

Restart the VS 2015 should fix this issue

How to make AJAX Call from POSTMAN

There are two types of RESTful Web Service methods can be consumed by ajax call: HttpPost and HttpGet.

for HttpGet, it’s pretty simple, all we need to do is add querystring parameters to the URL.

for HttpPost, if the Rest web service method take an object as parameter, we will need to construct the object as JSON and pass it in the body of the request. A key element to get it working is to add Content-Type: application/json to HEADER section.

Do NOT check Email first thing in the morning

Ignorance is Productive

When it comes to email, ignorance is bliss. That’s why if you’ve got something important you want to make progress on, I have these four words for you:

Don’t Check Your Email

as soon as you get up, work on something important for 30-45 minutes, and only then check it. If you can stand it, wait even longer.

And you know what? As long as you’re ignorant of everything else that’s going on outside, you can concentrate on what you want to work on.

Any new information you get can cause you to get distracted. On a quick tangent, this is also why I often don’t look at any news in the morning, don’t turn on the TV, and listen to audiobooks or even educational podcasts instead of the radio in my car – I don’t want anything to distract me. I can’t control everything but I can control my own.

It’s not Your Todo List

Do you know what is most important for you to work on? Do you know the first thing you want to do this morning? Then go ahead and do it!

On the other hand by checking email, you risk doing what someone else wants you to do. Every time you open an Email, you should consider whether it’s more important than everything else on your task list – but realistically, how many of us actually do that?

If you don’t, then the items you end up working on (even if it’s just replying and giving information) end up being tasks for other people rather than yourself.

Or more bluntly, when you check your inbox, the emails you get are a todo list someone else makes for you.

So, Who is in charge of your time – you, or the person emailing you?

It’s an excuse to Lack Direction

“Why are you checking email first thing in the morning anyway?”

Most likely the answer could be “you don’t know what you are supposed to be working on”

I am certainly not immune to this myself. If I am checking my inbox too often, that’s frequently an early warning sign that my todo list has gotten off track somewhere.

The real problem behind this behavior is that you don’t see checking email as a low priority activity, because you haven’t decided what the high priority activities area are. when you don’t have a clear list of priorities, checking email becomes an urgent activity that you do, but at the expense of your important ones.

If this strikes a nerve with you, don’t worry – it can be fixed. Find out Urgent versus Important time management matrix, and stop checking email so frequently.

Reaction or “Proaction”

when you check your email, the best case scenario is you checked at exactly the right moment, just when a super important email came in – and you can take instant action right away. How often does that actually happen? Rarely

The usual case is that, when you turn on your “check email” mode, you end up with more work to do, by replying emails regardless of their true priority.

I prefer taking proactive actions – what I call proaction. Work on the things that are important to you, regardless of whether they’re urgent or simply at the top of your inbox.

Searching for Excuses

If I’ blindly checking email, I am usually not checking for anything important – I am usually searching for an excuse to not do the work I know I must do.

I am searching for any reason why I can tell myself later I didn’t get the work done that needed to be.

Don’t fall in that trap. Don’t give yourself an out by checking your email for an excuse to fail.

It builds Expectation

A lot of people tell me “But I have to check my email! People expect a response from me”

First of all, I don’t believe it. If they do urgently awaiting your response, there are surly lots of ways to reach you, by phone, by visiting, by calling your colleague.

The more often you check email, the more often people will expect you to check it. and that’s the reason why people are EXPECTING response from you.

Just stop checking it first thing in the morning, and people won’t expect it anymore.

I know, it’s easier said than done. Don’t worry, after the first week or two, nobody will think anything of it.

Of course, there are causes you must check your email. well, if you do, constrain yourself to only check a limited subset of email, and I recommend you follow these rules

  1. Only check if there is something specific you are looking for or awaiting for
  2. Separate low value emails
  3. Set a time limit. Commit to checking for 5 minutes, just to look for that one piece of information, and you are done. before you open your inbox, decide what you will do if 1)the email is there 2)the email isn’t there 3)the email is incomplete. Don’t be reactionary – proactively decide what action you will take based on the outcomes you expect.


IoT: Monetizing the Internet of Things

IoT continues to evolve at a rapid pace, right in front of our very eyes. Supoposely,

  • By 2017, an estimated 90M people will live in smart homes.
  • By 2020, 50B connected devices is IoT

but there are challenges, especiallyu when it comes building a recurring revenue model that allows you to stay agile, respond to your market, and scale products quickly and successfully.

IoT is clearly the near future of business. But as we quickly progress into our increasingly digitized world, one that concentrates on connections – wireless, virtuals, etc. It’s super critical to focus on a solid business model will ensure your business gets a smart start on the right track.

the questions you have to understand and answer before you made any possible success in IoT

  1. How, if done right, IoT could mean massive growth opportunities for your business
  2. How can you successfully conquer the challenges of integrating products and services
  3. How companies like Nest, Honeywell, and Lowe’s have built powerful business models

the control collection cannot be modified during databind

In SharePoint, this error appears to be a visio web access web part, or Nintex workflow issue, is due to a “detail” of the master page applied.

the master page shows the control SPWebPartManager in the HEAD insteead of the BODY.

A start point on fixing this is move the SPWebPartManager control to body part in your master page. It works for me, in the case of Nintex workflow cause the issue.


Three pits on your way to setting up your business

I see lots of startups showing off their thoughts and sentiment, different style in quite significant way. some are heroic, some are coziness, some mooching, some solemn and stirring, and some are desperate. starting up a business is like marriage, looks great by stranger, but only the startups know what they have been through.

It’s been three years since my second startup, and I would like to talk about the starting up from my point of view. I divided the startup to three phases: the first phase is the first three month, and the second phase is the first year, and the third phase is the first three years. Normally if startup is still alive after three years, and have some reputation in the market, then this business has pass it’s critical stage, and start its next stage: growing stage. At this stage the business is not easy to die, but whether it can grow big, all depends on the industry and this business’ characteristic.

This first phase, i.e. the first three months, at this phase the startup only have an idea, no products have been formed yet, not even going though the market test out. The startup is just like a new solider, all day excited and vigorous. The startup either focus on products, contacting potential customer, or writing business plan, contacting investors. but all in all, the startup is very active and efficiency.

If thing goes well, after three months, the product should beginning to take shape, and got some investment if lucky. Now it’s time to start testing the product, and normally come with two outcomes: one is the product is very popular, although the probability is very small; another one is common situation, which it’s realized that it’s not as good as expected. the startup will experience their first strike, and part of startup will chose to quit, the others will chose to uphold their faith, and continuing to improve their products, or pick another direction to try again.

After the first three months, very few startup begin their fast growing phase, and these startup feel coziness and start feel it’s easy like piece of cake! but unfortunately most startup not that lucky, they start facing difficulty, and start realize that starting up a business is not as easy as they imagined. They must keeping amend and revise their products or business model, before they can survive in the market.

Keeping doing that for one year, few luckier become the rising star. They start the first round investment, and joining all sort of presentation, doing marketing through all different channels. However a majority of startups start fall in to mooching. It seems they are always one step behind after they have tried a few products and business models, and they don’t have too much room for any further improvement after the cash flow is tighter and team is under higher pressure. At this time, another wave of startups choose to quit, and the rest choose to keep fighting and searching for new direction.

From the first year to the third year, there is no big changes for these two years compared with the first year. If the business is still alive, it means the business has found it’s direction. They have successfully pull through infancy stage, and begin their preschool period. The products is in an early form, and have some reputation in the market, but the team begin to having problems. Because the rapid growth didn’t come together with management prompt, most startups don’t have management experience, or even despise the important of management and think management is equal to bureaucracy, the business start growing pain.

Statistically speaking, the average life of a business is 2.5 years, which means at least 50% of business can’t survive more than 2 years. It is hard to believe but it’s brutal truth. Before these business die, they will experience the most difficult phase –  solemn and stirring, and then becoming desperate. Some co-founders choose to quit and go back to big companies, or choose to pick next project. Only these startups insist can survive and growing, with lower profile.

I would like to say congratulation after three years, but don’t get excited too early, another three big challenges is awaiting: startups feel powerless in management, the co-founders are falling behind. Even through the business strategy is clear, but it’s always hard to carry out because lots of details issues start emerging. the organisation start facing problems from different facet, and always short on skilled resources, recruitment and keeping people is getting harder and harder. Organisation regulation become falling behind the business growth. Now the business face another transition.

If you think your business having lots of issues, don’t be depression, because lots of business having the same amount of issues. Keep in mind identifying and focusing on the few fatal issues, which can make your business survive. and then you can resolve other issues slowly during your development. The process of business growing is the process of solving problem, and it’s also the process of startups self-improvement and self-growth.

If you always have growth pain, it’s not a bad thing, because only live people can having the pain.

The Top 10 Mistakes That KnockoutJS Developers Make

1 Modules

Unlike other UI frameworks, Knockout does not come with a built in way to modularize your application. It’s possible to write an entire Knockout app in a single HTML file:


While this runs, it definitely won’t scale to applications of any significant complexity. The official Knockout docs suggest using RequireJS for Asynchronous Module Definition (AMD), and I wholeheartedly second this recommendation. Using RequireJS and the domReady module, the above code refactors into three separate files.







2 var self = this;

Keeping track of this in Knockout can be tough. Setting var self = this; at the top of every view model makes it easy.

For example, if var self = this; is not set then this must be passed into every computed observable:


Forgetting to pass in this is easy to do and can result in hard to track down bugs. Ifvar self = this; is set then passing this is not necessary:


var self = this; can also help avoid bugs when one binding context refers to another. Consider the following code that displays a list of names. When a user clicks on an name in the list, that name is displayed in the <span> below.





When selectPerson is called its scope is set to the object in person corresponding to the name clicked. However, because var self = this; is set the view model object is still accessible within the event callback. This would not be the case otherwise.

In production code I almost always define var self = this;. However, for the sake of brevity, I won’t use it in some examples in this article.

3 Logic in templates

Knockout makes it easy to write complicated logic in HTML templates. Avoid doing this at all costs! It results in difficult to test and maintain code. Instead of using logic in templates…


4 Testing

Speaking of testing, by default Knockout offers no tools to help you. This does not mean you shouldn’t write tests! There are ample JS testing frameworks, and you should be able to pick up and drop any of them into your Knockout application. As with anything, the earlier you start writing tests the better. I usually don’t start a new Knockout project without also including a testing framework.

5 ko.mapping

ko.mapping is a plugin for Knockout that makes working with data fetched from REST endpoints much more enjoyable.

Without ko.mapping, a view model that consumes objects from a REST API might look like this:

    function viewModel() {
        * Gets data about a person from the server:
        * person = {
        *   firstName: "John",
        *   lastName: "Stewart"
        * }
        var person = getPersonFromServer();

        this.person = {};
        this.person.firstName = ko.observable(person.firstName);
        this.person.lastName = ko.observable(person.lastName);

With ko.mapping the view model is much simpler:

    function viewModel() {
        var person = getPersonFromServer();
        this.person = ko.mapping.fromJS(person);

Want to convert part of the view model back to plain JSON so that you can POST it back to the API? That’s a one-liner too:

    var json = ko.mapping.toJS(this.person);

While ko.mapping is to some degree officially part of Knockout (it’s in the official documentation), it is a separate project that you’ll have to download and include.

It’s also worth nothing that some people prefer the functionally analogousko.viewModel plugin to ko.mapping. ko.mapping has always worked fine for me, but it only seemed fair to link to both. Use one or the other, but don’t use neither!

6 textInput and valueUpdate

This may seem minor, but it’s caused me so many headaches that it’s worth including. Knockout binds the value of input elements a somewhat strange way. To illustrate, let’s say we have an input element and want to update some text on the page in real time as the input’s value changes:

    <input type="text" data-bind="value: myValue">
    Value: <span data-bind="text: myValue"></span>
    function viewModel() {
        this.myValue = ko.observable();

Surprisingly, the above won’t work. The myValue observable (and thus our text in the span) updates whenever the input loses or gains focus, not as it’s value changes. Why? For performance reasons this is how Knockout behaves by default.

To fix this in Knockout 3.2 (current at the time of writing) or newer, use the textInput binding instead of the value binding.

    <input type="text" data-bind="textInput: myValue">

This will provide immediate updates to myValue with the minor caveat that it won’t guarantee that the value attribute of the input is always synced with myValue.

If you are using an older version of Knockout or if you are dead set on using the value binding, then you must use the valueUpdate flag.

    <input type="text" data-bind="value: myValue, valueUpdate='afterkeydown'">

In Knockout 3.2 there are 4 possible values for valueUpdate, each with its own idiosyncrasies:

  • + input – Updates when the value of the element changes. Doesn’t work in IE8-.
  • + keyup – Updates when a keyup event is fired
  • + keypress – Updates when a keypress event is fired.
  • + afterkeydown – Updates as soon as the user starts typing a character. Does not work on all mobile browsers — notably Safari on IOS7.

Using the textInput binding is strongly recommended over using the valueUpdateflag.

7 Don’t repeatedly push into observable arrays

Pushing multiple times into observable arrays can cause significant performance issues with your application:

    function viewModel() {
        var arr = [0, 1, ..., 999];

        this.numbers = ko.observableArray();

        for (var i = 0; i < arr.length; i++) {

Running the for loop above will cause Knockout to redraw the page 1000 times — one for each push. To avoid this, simply overwrite the old value of our entire array:

    function viewModel() {
        var arr = [0, 1, ..., 999];
        this.numbers = ko.observableArray(arr);

To transform data before putting it into our new array, use ko.utils.arrayMap.

    function Number(number) {
        this.number = number;

    function viewModel() {
        var arr = [0,1, ..., 999];

        // creates an array of Number objects
        this.numbers = ko.observableArray(ko.utils.arrayMap(arr, function(number) {
            return new Number(number)


To append many items to an existing observable array, exploit the fact that pushaccepts a variable number of arguments and use apply to push them in all at once.

    function viewModel() {
        var arr = [500, 501, ... 999];

        this.numbers = ko.observableArray([0, 1, ..., 499]);
        this.numbers.push.apply(self.numbers, arr);

8 Observable arrays don’t automatically have observable members

Observable arrays track changes to which objects are in the array. They do not track changes to the state of those objects.

    <ul data-bind="foreach: people">
        <li data-bind="text: name"></li>
    <button data-bind="click: makeDerekMike">Make Derek Mike</button>
    function viewModel() {
        var self = this;

        self.people = ko.observableArray([
                name: 'Derek',
                name: 'Sara'

        self.makeDerekMike = function() {
            for (var i = 0; i < self.people().length; i++) {
                if (self.people()[i].name === 'Derek') {
                    self.people()[i].name = 'Mike';

Clicking the button in the first example will not trigger a page refresh despite the fact that it will modify an object in the array underlying people. This is because the same objects still belong topeople. To trigger a page refresh, we need to explicitly make the fields of the elements in people observable:

    function viewModel() {
        var self = this;

        self.people = ko.observableArray([
                name: ko.observable('Derek')
                name: ko.observable('Sara')

        self.makeDerekMike = function() {
            for (var i = 0; i < self.people().length; i++) {
                if (self.people()[i].name() === 'Derek') {

9 Components

Because Knockout makes building interactive widgets so simple, it’s easy to write similar code in different parts of your application. Use Knockout components to abstract common UI widgets and promote code reuse.

Using components, we can build a simple reusable list builder as follows:

    <span>This is a list with no initial values</span>
    <div data-bind="component: 'list-builder'"></div>

    <span>This is a list with some initial values</span>
    <div data-bind="component: {
        name: 'list-builder',
        params: { list: ['item', 'another item'] }
    function Item(text) {
        this.text = text;

    ko.components.register('list-builder', {
        viewModel: function(params) {
            var self = this;

            self.list = ko.observableArray([]);

            if (params && params.list) {
                self.list(ko.utils.arrayMap(params.list, function(item) {
                    return new Item(text);

            self.newText = ko.observable();
            self.add = function() {
                self.list.push(new Item(text));
            '<ul data-bind="foreach: list">' +
                '<li data-bind="text: text"></li>' +
            '</ul>' +
            '<input type="text" data-bind="textInput: newText" />' +
            '<button data-bind="click: add">Add</button>'

Note that you probably don’t want to inline the viewModel and template as above in any production code code. Fortunately, this can be solved using require.js (see #1). For a description of how to do this check out the official components documentation.

10 Tutorials

Knockout the official tutorials are great! They offer a interactive sandbox to play around with the framework in a guided fashion.

Error on Installing Umbraco with Visual Studio

I got the error when installing Umbraco v7.2.6 to Visual Studio 2013 MVC project.

Updating ‘Microsoft.AspNet.Mvc 5.2.3’ to ‘Microsoft.AspNet.Mvc 4.0.20710.0’ failed. Unable to find a version of ‘UmbracoCms.Core’ that is compatible with ‘Microsoft.AspNet.Mvc 4.0.20710.0’.

To fix this issue, install the package “Microsoft.AspNet.Mvc.FixedDisplayModes” first, and then run Install-Package UmbracoCms

Top 10 ASP.NET MVC Best Practices

In this section we will discuss 10 best practices and tips we should keep in mind when working with ASP.NET MVC applications.

Tip 1: Disable Request Validation

Request Validation is a feature that prevents potentially dangerous content from being submitted. This feature is enabled by default. However, at times you might need your application to post HTML markup tags to the server. You would then need this feature to be disabled. Here is how you can do it:

public ActionResult Create([Bind(Exclude=”Id”)]Employee empObj)


Tip 2: Cache Your Data

You can improve your application’s performance to a considerable extent by caching relatively stale data. That way the network bandwidth between the client and the server is also reduced. It is great if you can also cache the rendered action of web pages that are relatively stale, i.e., don’t change much over time.

public class HomeController : Controller
public ActionResult Index()


Tip 3: Isolate Data Access Logic From the Controller

The Controller in an ASP.NET MVC application should never have the Data Access logic. The Controller in an ASP.NET MVC application is meant to render the appropriate view based on some user interface action. You should make use of Repository Pattern to isolate Data Access Logic from the Controller – you might need dependency injection to inject the appropriate Repository to your controller at runtime.

Tip 4: Using a Master View Model

We frequently use Master Pages in ASP.NET applications – the same Master Page would be extended by the Content Pages throughout the application to give a similarity as far as look and feel and functionality is concerned. How do we do that in an ASP.NET MVC application? Well, we need a MasterViewModel similar to what is shown in the code snippet below:

public class ViewModelBase
public ViewModelBase()

//Other methods and properties

Tip 5: Use Strongly Typed Models

A strongly typed view is a view that defines its data model as a CLR type instead of a weakly typed dictionary that may contain potentially anything. To create a strongly typed view, check the “Create a strongly-typed view” checkbox while you are creating the view. If you plan to create a strongly typed view manually later, ensure that your view “Inherits” System.Web.Mvc.<Your Namespace>.<YourClass>

Tip 6: Use Data Annotations for Validation

You can make use of the System.ComponentModel.DataAnnotations assembly to validate your server – side code by simply decorating your model with the necessary attributes. Here is an example:

public class Employee
[Required(ErrorMessage=”Employee Name Cannot be Blank”)]
public string Name { get; set; }

// …

Tip 7: Take Advantage of Model Binding

Consider the following code snippet:

public ActionResult Create()
Employee employee = new Employee();
employee.Name = Request.Form[“Name”];

// …

return View();

You can make use of model binder to save you from having to use the Request and HttpContext properties – just use FormsCollection instead. Here is an example:

public ActionResult Create(FormCollection values)
Employee employee = new Employee();
employee.Name = values[“Name”];

// …

return View();

Tip 8: Cache Pages that Contain Shared Data or are Public and don’t Require Authorization

You should not cache pages that need authorization in ASP.NET MVC. You should not cache pages that contain private data or need authorization. Caching pages in ASP.NET MVC is simple – just specify the OutputCache directive as shown in the code snippet below:

[OutputCache(Duration = 60)]
public ActionResult Index()
return View(“Index”, somedata);

Tip 9: Use Extension Methods

You can make use of Extension Methods to simplifies use of LINQ queries that boost application performance too. This can dramatically reduce the amount of code that you would need to otherwise write when writing your LINQ queries, make your LINQ queries manageable and also improve the application’s performance.

Tip 10: Take Advantage of Model Binding

You can take advantage of Microsoft Velocity – a distributed caching engine to boost the application performance of your ASP.NET MVC applications. You can learn more on Velocity from this link: