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If you are a developer faced with a peculiar scenario that an existing WCF library needs to be ported to your new web application without any server side code and without any changes to the existing WCF code then please do read on.

A developer has an existing WCF program running flawlessly with WPF or WinForm client, now that same program needs to be ported to a web application. He has been tasked to create a HTML/JS view to represent the data. For simplicity sake lets assume that on the client side there is a text box and a drop down list. Each time you type a letter in the textbox, the drop down list(combobox/select) is populated with company names matching to the text entered in the box.

In the image below I have typed "X" in the text box and the dropdown(combobox/select) is automatically populated with server side data which has X in it.

 

 So how do we go about achieving this.?

• Create a web application in Visual Studio WebForm or MVC as view engine, it should not matter but I have used WebForms in the demo.
• Add a default aspx page 
• Add an Interface file and then paste in this code

• As you can guess I have created a very simple Company class which will act as my "DataContract". Code for the same is given below.

• We must create a class which implements the interface. For demo purpose the list of company names are a static list, for your own experiment you may get this data from a database.
• The important part starts here we cannot use a simple class file , instead we must add a text file and rename it to AddressServer.svc
• This file by itself only has a single line of markup.
  <%@ ServiceHost Service="SampleWCFJS.Service.AddressService" Factory="System.ServiceModel.Activation.WebScriptServiceHostFactory" language="C#" CodeBehind="~/AddressServer.svc.cs" debug="true" %>
• Let us add another text file and rename it AddressServer.svc.cs, this is the code behind file which will implement our Service contract class. In this file (AddressServer.svc.cs), paste in the following code

 

 

 

 

• We must get some W.C.F configurations in place in our Web.config file. Most of it must be known to you. Only a couple of tweaks are needed to make this code work with Javascript/jQuery.

• In the solution explorer go to to the AddressServer.svc file, right click on it and choose "view in browser". If you have done everything as explained then the browser will show a page similar to this

• If you see this page then the first step has been successful. Next step is to get the JavaScript proxy to be used with our client script.
• Just change the URL on your browser by adding a jsdebug switch. As shown below

http://localhost:44856/AddressServer.svc

http://localhost:44856/AddressServer.svc/jsdebug

• The browser will either list out JavaScript on the screen or offer to download it. In any case just save it in your web application folder by the name of jsdebug.js, this name is completely dependent on you. Nothing special about the name.
• Let us create the front end or the aspx which we are going to use to test out our concept. Add the following lines to the body of Default.aspx page, if you don't have one , please go ahead and add a web form

• Pretty simple code, a html input of text type and a combobox(select), I have called a function getCompanies() which will be defined in Javascript, it will be called each time a keyup event happens in the text box.
• For demo purpose I will write the Javascript code in the head section but as you might be aware, it is increasingly the standard to keep all Javascript related stuff as the last line of the body tag.

• There are a couple of points to note, firstly I have added the reference to the script file which contains the proxy class code and was automatically generated for me when I had added jsdebug switch to the service URL. 
• Secondly I have added reference to jQuery.js and MicrosoftAjax.js, both of these files are available on NuGet, so it is pretty self explanatory that you need to grab these two from NuGet or download it from their respective vendor websites.
• Again the function gets called when a keyup event happens, it instantiates an object of the WCF service class, then uses the object to call the function in it, passing to the function the current value of the textbox and the call back to onsuccess function and on fail function.
• If the WCF service call is successful then in my code the successAutoComplete() function gets called which will have the array of Company objects with names  matching the string entered in the textbox.
• Next step is to remove all the current contents of the combo box(select), loop through the result array and add the company names to the combo box.
• That's it, you have successfully called a W.C.F service from JavaScript using jQuery. Run the Default.aspx page in the browser and type in some text in the input box(textbox). Immediately the dropdown(combobox/select) is populated with related data from server.