Thursday, October 23, 2014

Application UI hangs on long running operation in C# WindowsForm and WPF (BackgroundWorker in C#)

Once i came across a scenario in a Windows Presentation Foundation where on click of a button i needed to call a Restful Service which returns JSON and then i needed to deserialize the JSON and do soemthing with that, but when i wrote the code in the button event, it worked successfully but one thing that i noted that unitl the all operation completes my button remains pressed and UI also not responsive , so after researching a little i came to know this:

When we have some long running code that can take much time than normal time we should execute in a background thread not on UI thread, becasue executing it in UI thread will make our application un responsive and user will get irritated, here is my code which was executing directly on UI thread in button event:



This worked fine but as it is executing all the code on UI thread the application becomes unresponsive and user has to wait for the process to complete which is not a good user experience in any software or web application, after a  little reasearch i came to know about BackgroundWorker class which executes the code in separate thread not in UI thread.

This is the first version in which it was all happening on the UI thread all was fine but my button state was in pressed state and UI blocked until the service call completed and GridView populated.


private void btnLookup_Clicked(object sender, RoutedEventArgs e)
{

    string url = "http://www.lyfechannel.com/channels/allscripts/allscripts_institutions.php?allscripts=XXXX&user=YYYY&password=ZZZZ";

    WebRequest request = WebRequest.Create(url);

    request.Timeout = 500000;

    WebResponse response = request.GetResponse();

    var reader = new StreamReader(response.GetResponseStream());

    string json = reader.ReadToEnd();

    var jsonAsCSharp = JsonConvert.DeserializeObject<JSONWrapper>(json);

    PatientGrid.DataSource = jsonAsCSharp.Patients;
}

Now i am showing the version in which i used BackgroundWorker class, First of all create BackgroudWorker instance assign its events:


private void MyMethodToCallExpansiveOperation()
{
    //Call method to show wait screen
    BackgroundWorker workertranaction = new BackgroundWorker();
    workertranaction.DoWork += new DoWorkEventHandler(workertranaction_DoWork);
    workertranaction.RunWorkerCompleted += new RunWorkerCompletedEventHandler(
        workertranaction_RunWorkerCompleted);
    workertranaction.RunWorkerAsync();
}

Now write the expensive operation code in workertranaction_DoWork method:


private void workertranaction_DoWork(object sender, DoWorkEventArgs e)
{
    string url ="http://www.lyfechannel.com/channels/allscripts/allscripts_institutions.php?allscripts=XXXX&user=YYYY&password=ZZZZ";

    WebRequest request = WebRequest.Create(url);

    request.Timeout = 500000;

    WebResponse response = request.GetResponse();

    var reader = new StreamReader(response.GetResponseStream());

    string json = reader.ReadToEnd();

    var jsonAsCSharp = JsonConvert.DeserializeObject<JSONWrapper>(json);

    patients = jsonAsCSharp.Patients;
}


and in  workertranaction_RunWorkerCompleted  bind List of Patients with Grid, as Do_Work does not executes in UI thread so we cannot access them in this method:


private void workertranaction_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
    PatientGrid.DataSource = patients;
}

Now on button click we need to just call MyMethodToCallExpansiveOperation method:


private void btnLookup_Clicked(object sender, RoutedEventArgs e)
{
    MyMethodToCallExpansiveOperation();
}

Wednesday, October 15, 2014

difference between ~= and *= in jquery

Few days back, i saw a SO question, that what is the difference between [attribute~=value] and [attribute*=value]?



*= is attributeContains selector , From jquery docs:
Selects elements that have the specified attribute with a value containing a given substring.
~= is attributeContainsWord selector , From jquery docs:
Selects elements that have the specified attribute with a value containing a given word, delimited by spaces.


The attributeContains selector is for the string to be contained in the attribute value while attributeContainsWord selector is for string seperated with delimeted space. The official jquery examples clearly explain it.



Attribute Contains Selector [name*="value"]

HTML:

<input name="man-news">
<input name="milkman">
<input name="letterman2">
<input name="newmilk">
JQUERY:

$( "input[name*='man']" ).val( "has man in it!" );
OUTPUT:


Here is the fiddle demonstrating the Attribute Contains Selector [name*="value"] behavior

Attribute Contains Word Selector [name~="value"]

HTML:

<input name="man-news">
<input name="milk man">
<input name="letterman2">
<input name="newmilk">
JQUERY:


$( "input[name~='man']" ).val( "mr. man is in it!" );

OUTPUT:

Here is example demonstrating the behavior of  Attribute Contains Word Selector [name~="value"] 

Saturday, September 27, 2014

Deserializing JSON returned by Restful Service in C#

Nowa days Restful services are more used which mostly return xml or json as reponse. The advantage of restful services are platform independence, a service made restful can be accessed from any platform like Java, c#,php, ruby etc.


I have a service  at this url : http://www.lyfechannel.com/channels/allscripts/allscripts_institutions.php?allscripts=XXXX&user=YYYY&password=ZZZZ  which returns following json as response:


{
"connections":"72", 
"incomplete":"319", 
"qualified":"14", 
"loggedin":"Dr. Frederick Banting | One Medical | San Francisco, Embarcadero", 
"red": "40", 
"yellow": "12", 
"green": "20"
}

First of all we need to create a C# class for deserializing json  to that spcific type, the current json object is not very complex so we can easily write class against this json with properties but mostly we will not have json simple like this, so most of the time i use json2csharp.com to generate classes against the json returned by service.


Our class for this json will look like this:


public class JSONWrapper
{
   public string connections { get; set; }
   public string incomplete { get; set; }
   public string qualified { get; set; }
   public string loggedin { get; set; }
   public string red { get; set; }
   public string yellow { get; set; }
   public string green { get; set; }
}

For deserializing json we have a library available Newtonsoft JSON which we will use for deserializing json to specific type.

We can install it in our project by going to Nuget Package Manager Console in Tools of Visual Studio and writing this command on Nuget Package Manager Console:

PM> Install-Package Newtonsoft.Json 

 If you have dll downloaded on your system you can also add reference by going in to References and click Add Reference from context menu:


 After clicking Add Reference browse to the location where the dll is present and check it and click ok.



Now we will write the code to call the specific url and we will deserialize the returned response to the specific class.


Here we go:


using System;
using System.IO;
using System.Net;
using Newtonsoft.Json;

class Program
{
   static void Main(string[] args)
   {
      try
      {
          string url = "http://www.lyfechannel.com/channels/allscripts/allscripts_institutions.php?allscripts=XXXX&user=YYYY&password=ZZZZ";

          WebRequest request = WebRequest.Create(url);

          request.Timeout = 500000;

          WebResponse response = request.GetResponse();

          var reader = new StreamReader(response.GetResponseStream());

          string json = reader.ReadToEnd();

          var jsonAsCSharp = JsonConvert.DeserializeObject<JSONWrapper>(json);

          Console.WriteLine(jsonAsCSharp);
       }

      catch (Exception e)
      {
         Console.WriteLine("Error Occured:"+e.Message);
      }
   }
}


Here is the  attached sample project console application

Sunday, September 21, 2014

Error 25 The type of one of the expressions in the join clause is incorrect. Type inference failed in the call to 'Join'

I had a scenario where i needed to fetch Result Data from multiple tables on basis of some condition by applying joins between the tables using Entity Framework. I was using Linq queries as in EF linq query is faster than the normal string queries and stored procedures, but i was getting the exception.

Here is the query which i wrote:

I made the object of my EntitiesClass generated by EDM:


OLSContainer ols = new OLSContainer();
        var reSet = from l in ols.LEVEL_COURSE
                    join lp in ols.PACKAGES 
                    on new { l.course_ID, l.levelID } 
                    equals new { lp.course_ID, lp.level_ID }
                    select l; 
which i know was wrong and on this query i was getting this exception:

Error 25 The type of one of the expressions in the join clause is 
incorrect. Type inference failed in the call to 'Join'

The mistake i was making was pretty was pretty simple in this scenario i dont need the join because i was only selecting data from LEVEL_COURSE table which can be achieved by simple where clause in the current scenario like this:



OLSContainer ols = new OLSContainer();
        var reSet = (from l in ols.LEVEL_COURSE
                    from p in ols.PACKAGES
                    where l.course_ID == p.course_ID 
                    &amp;&amp; l.levelID == p.level_ID 
                    &amp;&amp;    l.course_ID==courseID
                    select new { l.levelID, l.levelName }).Distinct();

This solved my problem and the exception that i was getting was due to column names were same. My  PACKAGES table and LEVEL_COURSE table both have column named course_ID which were of same datat type as well so it was confusing compiler to take which one, but at last i got working thing as i needed.


Reference Link:

http://stackoverflow.com/questions/14273879/error25the-type-of-one-of-the-expressions-in-the-join-clause-is-incorrect-typ/14290833#14290833

Sql NOT IN operator in LINQ query Entity Framework

Few days ago, i came across a scenario in which i needed to apply sql NOT IN operator in my project as LINQ Query, my project was in mvc and i used ADO.net Entity Data Model to interact with database.


Here is the sql query which i needed to convert to linq:


SELECT d.processid,d.name,t.test_name
FROM dc_tp_tprocess d
left outer join dc_tp_tprocedured pd on pd.processid=d.processid
left outer join dc_tp_test t on t.procedureid=pd.procedureid
where d.active='Y' and t.testid=1 
                   and d.processid not in (1,2,6,8,9,10)
order by t.testid,d.processid 


At last after posting my question on a forum i got an answer from some one and that was this:


int[] tmp=new int[]{1,2,6,8,9,10};

var query=from d in dc_tp_tprocess
          join pd in dc_tp_tprocedured on d.processid equals pd.processid&nbsp;
         into leftGroup1
          from pd in leftGroup1.DefaultIfEmpty() 
          join t in dc_tp_test on pd.procedureid equals t.procedureid&nbsp;
          into leftGroup2
          from t in leftGroup2.DefaultIfEmpty()
          orderby t.testid,d.processid
          where d.active=="Y"&nbsp;
         &amp;&amp; t.testid==1&nbsp;
         &amp;&amp; !tmp.Contains(d.processid)
          select new {d.processid,d.name,test_name=t==null?"":t.test_name}; 


The tmp is a temporary array taken from which i am checking that the processID coming in the current row not exists in that array then select row.

I hope it will help if you stuck or got same scenario and don't getting how to handle the situation -:).

Friday, September 12, 2014

How to Deserialize Xml using LINQ

Binding XML data to Model in C# MVCToday i saw a SO question where OP had xml in a string and OP wanted to deserialize to its specifc type using linq.

Here is the xml:


<people>  
            <person>
                <name>Mr Brown</name>
                <age>40</age>
                <hobby>
                    <title>Eating</title>
                    <description>eats a lot</description>
                </hobby>
                <hobby>
                    <title>Sleeping</title>
                    <description>sleeps a lot</description>
                </hobby>
            </person>
            <person>
                <name>Mr White</name>
                <age>40</age>
                <hobby>
                    <title>Skiing</title>
                    <description>more details on this</description>
                </hobby>
                <hobby>
                    <title>Football</title>
                    <description>watches football</description>
                </hobby>
            </person>
            </people>

First of all we need to create class type in which the data will be deserialized.We have main node people so our one class will be People with three properties Name,Age and Hobbies.As hobbies can be multiple of a person we will need a collection of hobbies and you can observe that from the xml as well that person have multiple hobbies and of course i also have many hobbies..:)


here it is:


public class People
        {
            public string Name { get; set; }
            public string Age { get; set; }
            public IList<Hobby> Hobbies { get; set; }
        }
        public class Hobby
        {
            public string Title { get; set; }
            public string Description { get; set; }
        }

First of all i will load the string xml in to XElement :


string xml = @"<people>  
            <person>
                <name>Mr Brown</name>
                <age>40</age>
                <hobby>
                    <title>Eating</title>
                    <description>eats a lot</description>
                </hobby>
                <hobby>
                    <title>Sleeping</title>
                    <description>sleeps a lot</description>
                </hobby>
            </person>
            <person>
                <name>Mr White</name>
                <age>40</age>
                <hobby>
                    <title>Skiing</title>
                    <description>more details on this</description>
                </hobby>
                <hobby>
                    <title>Football</title>
                    <description>watches football</description>
                </hobby>
            </person>
            </people>";

XElement element=XElement.Parse(xml);

Now we will write linq query to deserialize the xml. Here we go:


var person = from a in element.Descendants("person")
             select new People
             {
              Name = a.Element("name").Value,
              Age = a.Element("age").Value,
              Hobbies = a.Descendants("hobby")
                         .Select(x => new Hobby
                                 {
                                  Title = x.Element("title").Value,
                                  Description = x.Element("description").Value
                                 }).ToList()
                            };
  
foreach(var d in person)
{
  
  Console.WriteLine(String.Format("Name = {0}:Age={1}:Hobbies:{2}",d.Name,d.Age,d.Hobbies.Count()));
  
}

Here is theWorking Example on DOT NET FIDDLE of the code.


Cheers! Happy Coding.

Stackoverflow Reference Question:

Binding XML data to Model in C# MVC

Thursday, September 11, 2014

Javascript deep Copy Array (Clone Javascript array without reference)

Today i saw a SO question, in which the OP was asking about how to clone a javascript array in a variable so that it does not have reference tot the original array.


Here is the scenario:


var fruit = function (name){
    this.name = name;
}
var fruits = [];
fruits.push(new fruit('apple'));
fruits.push(new fruit('banana'));
fruits.push(new fruit('organge'));

var fruits2 = fruits;
fruits2.length = 0;

Now in the above when we assign fruits to fruits2, fruits2 actually has the reference of fruits, after that line if you see we are emptying the fruits2 array by setting its lenght to 0. But it will also make fruits array empty as well.


See here in the JSFiddle DEMO:

Now we have to make a way to do deep clone of array so that it not refers to original array, we can do it using slice() function of javascript.

Summary of slice():

The slice() method returns a shallow copy of a portion of an array into a new array object.

Description:

slice does not alter the original array, but returns a new "one level deep" copy that contains copies of the elements sliced from the original array. Elements of the original array are copied into the new array as follows:
  • For object references (and not the actual object), slice copies object references into the new array. Both the original and new array refer to the same object. If a referenced object changes, the changes are visible to both the new and original arrays.
  • For strings and numbers (not String and Number objects), slice copies strings and numbers into the new array. Changes to the string or number in one array does not affect the other array.

EXAMPLE:




// Our good friend the citrus from fruits example
var fruits = ['Banana', 'Orange', 'Lemon', 'Apple', 'Mango'];
var citrus = fruits.slice(1, 3);

// puts --> ['Orange','Lemon']

When we write slice(0)  , it returns the complete array shallow copy in return so our modified code will be:

 

var fruit = function (name){
    this.name = name;
}
var fruits = [];
fruits.push(new fruit('apple'));
fruits.push(new fruit('banana'));
fruits.push(new fruit('organge'));

var fruits2 = fruits.slice(0);
fruits2.length = 0;
console.log(fruits);

Here is the UPDATED FIDDLE  in which you can see it live working.