Friday, April 25, 2014

Call a method after multiple AJAX requests are finished through jQuery

You may face a situation where you need to make multiple AJAX requests and call your function after all those requests are completed.

jQuery provides a way to handle this neatly:


$.when($.ajax( "/page1" ), $.ajax( "/page2" ) ).then(function( a1, a2)
{
    // a1 and a2 are arguments resolved for the page1 and page2 ajax requests
    // Each argument is an array with the following structure: [ data, statusText,jqXHR ]
});

Friday, April 18, 2014

CSS media queries for different Internet Explorer versions

/* IE6/7 uses media, */
@media, { 
.container { color: green; } 
.item { color: red; }
} 

/* IE8 uses \0 */
@media all\0 { 
.container { color: brown; }
.item { color: orange; }} 

/* IE9 uses \9 */
@media all and (monochrome:0) { 
.container { color: yellow\9; }           .
.item { color: blue\9; }} 

/* IE10 and IE11 both use -ms-high-contrast */
@media all and (-ms-high-contrast:none)
 {
 .foo { color: green } /* IE10 */
 *::-ms-backdrop, .foo { color: red } /* IE11 */
 }

Tuesday, April 8, 2014

JSONP calls in ASP.NET MVC

JSONP is "JSON with padding".  It is used to access or transfer data across the domains.  The code below is used to access JSONP data from a remote server and fetch the results in ASP.NET MVC

public ContentResult FetchData()
        {
            string signedUrl = ""; //URL to fetch jsonp data from
            WebRequest request = (HttpWebRequest)WebRequest.Create(signedUrl);
            request.Method = WebRequestMethods.Http.Get;
            string result = string.Empty;

            using (var response = (HttpWebResponse)request.GetResponse())
            {
                using (var reader = new StreamReader(response.GetResponseStream()))
                {
                    result = reader.ReadToEnd();
                }
            }

            return Content(result, "application/javascript");
        }

Tuesday, March 25, 2014

Make the layout of controls same in all the browsers - UniformJS

Most of the developers must have faced an issue from their client to make the layout of the controls similar in all the browsers.

I recently came across a beautiful and simple plugin which would take care of the UI just by a single line of code.

The implementation is very simple:
<!-- Make sure your CSS file is listed before jQuery -->
<link rel="stylesheet" href="uniform.default.css" media="screen" />
<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.8/jquery.min.js"></script>
<script src="jquery.uniform.js"></script>]
// Style everything
$("select, input, a.button, button").uniform();

jQuery cross domain requests with JSONP

jQuery has a provision to make a cross domain AJAX request (GET) and fetch data in JSONP format.

$.ajax({
            type: 'GET',
            url: 'URL to access data',
            contentType: "application/json",
            crossDomain: true,
            cache: true,
            dataType: 'jsonp',
            success: function (result) {
            },
            error: function (e) {
                console.log(e.message);
            }
        });



Even if there is an error handler attached to the ajax call above, cross domain requests won't    handle any error or exceptions.  This is a limitation for jQuery JSONP calls.

Tuesday, February 18, 2014

LINQ - Filter a List from a comma separated string

I've used a sample Product class shown below.  productList contains 3 static values.

public class Product
{
    public int ProductId { get; set; }
    public string Name { get; set; }
    public decimal Price { get; set; }
}


string productIds = "1,3";
List<Product> productList = new List<Product>();

productList.Add(new Product() { Name = "iPhone", Price = 60000, ProductId = 1 });
productList.Add(new Product() { Name = "Google Nexus 5", Price = 34000, ProductId = 2 });
productList.Add(new Product() { Name = "iPad", Price = 27000, ProductId = 3 });


ProductIds are split into an IEnumerable<int> array and LINQ WHERE clause is used with "Contains"

//split productIds and populate productIdArray
IEnumerable<int> productIdArray = productIds.Split(',').Select(x => int.Parse(x));

//filter productList and fetch only the records which contains values in "productIdArray"
IEnumerable<Product> productFilter = productList.Where(c => productIdArray.Contains(c.ProductId));

"Children could not be evaluated" issue after updating Entity Framework to version 6

I was recently working on an ASP.NET MVC 4 website using Entity Framework 5.0.  

I updated my entity framework using "update-package -EntityFramework" command in package manager console.  It updated Entity Framework pretty well, but stuck me with an issue.  I was no longer able to debug my values and it showed "Children could not be evaluted" as shown below.  This was working fine before I updated my entity framework.








The solution is really simple but tricky.  I just had to add .ToList() at the end of the query and it worked like a charm.