Why/Where do We need Web Services?

You can use the Web Services for the following requirements.

1. Web API : Where you need to expose your service to others such as Payment Gateway, Travel and Cinema Bookings.. etc.,
2. Mobile Development: Web Service consume by Android and iOS Devices (Mobile, Tablet)
3. Cross Platform Applications: ASP.NET Web Services can consume by Java, PHP appications
4. Same Platform but diffrent applications: Windows Applications, Web Applications and Windows Serivces

SOAP vs REST (differences)

I have read articles about the differences between SOAP and REST as a web service communication protocol, but I think that the biggest advantages for REST over SOAP are:

1. REST is more dynamic, no need for creating and updating UDDI.
2. REST is not restricted to XML format. REST web services can send plain text, JSON, and also XML.

But SOAP is more standardized (Ex; security).

SOAP and REST can't be compared directly, since the first is a protocol (or at least tries to be) and the second is an architectural style. This is probably one of the sources of confusion around it, since people tend to call REST any HTTP API that isn't SOAP.

Pushing things a little and trying to establish a comparison, the main difference between SOAP and REST is the degree of coupling between client and server implementations. A SOAP client works like a custom desktop application, tightly coupled to the server. There's a rigid contract between client and server, and everything is expected to break if either side changes anything. You need constant updates following any change.

A REST client is more like a browser. It's a generic client that knows how to use a protocol and standardized methods, and an application has to fit inside that. You don't violate the protocol standards by creating extra methods, you leverage on the standard methods and create the actions with them on your media type. If done right, there's less coupling, and changes can be dealt with more gracefully. A client is supposed to enter a REST service with zero knowledge of the API, except for the entry point and the media type. In SOAP, the client needs previous knowledge on everything he will be using, or it won't even begin the interaction. Additionally, a REST client can be extended by code-on-demand supplied by the server itself, the classical example being javascript code used to drive the interaction with another service on the client-side.

I think these are the crucial points to understand what REST is about, and how it differs from SOAP:

• REST is protocol independent. It's not coupled to HTTP. Pretty much like you can follow an ftp link on a website, a REST application can use any protocol for which there is an standardized URI scheme.
• REST is not mapping CRUD to HTTP methods. Read this answer for a detailed explanation on that.
• REST is as standardized as the parts you're using. Security and authentication in HTTP is standardized, so that's what you use when doing REST over HTTP.
• REST is not REST without HATEOAS. This means that a client only knows the entry point URI and the resources are supposed to return links the client should follow. Those fancy documentation generators that give URI patterns for everything you can do in a REST API miss the point completely. They are not only documenting something that's supposed to be following the standard, but when you do that, you're coupling the client to one particular moment in the evolution of the API, and any changes on the API have to be documented and applied, or it will break.
• REST is the architectural style of the web itself. When you enter Stack Overflow, you know what a User, a Question and an Answer are, you know the media types, and the website provides you with the links to them. A REST API has to do the same. If we designed the web the way people think REST should be done, instead of having a home page with links to Questions and Answers, we'd have a static documentation explaining that in order to view a question, you have to take the URI sandeeprauniyar.com/questions/<id>, replace id with the Question.id and paste that on your browser. That's nonsense, but that's what many people think REST is.

This last point can't be emphasized enough. If your clients are building URIs from templates in documentation and not getting links in the resource representations, that's not REST. Roy Fielding, the author of REST, made it clear on this blog post: REST APIs must be hypertext-driven.

With the above in mind, you'll realize that while REST might not be restricted to XML, to do it correctly with any other format you'll have to design and standardize some format for your links. Hyperlinks are standard in XML, but not in JSON. There are draft standards for JSON, like HAL.

Finally, REST isn't for everyone, and a proof of that is how most people solve their problems very well with the HTTP APIs they call REST and never venture beyond that. REST is hard to do sometimes, especially in the beginning, but it pays over time with easier evolution on the server side, and client's resilience to changes. If you need something done quickly and easily, don't bother about getting REST right. It's probably not what you're looking for. If you need something that will have to stay online for years or even decades, then REST is for you.

Asp.net WebService or Creating and Consuming WebService in asp.net or Create and call webservice in asp.net or how to create webservice and how to use webservice in asp.net

What is Web Service?

Web Service is an application that is designed to interact directly with other applications over the internet. In simple sense, Web Services are means for interacting with objects over the Internet. The Web serivce consumers are able to invoke method calls on remote objects by using SOAP and HTTP over the Web. WebService is language independent and Web Services communicate by using standard web protocols and data formats, such as

• HTTP
• XML
• SOAP

Advantages of Web Service

Web Service messages are formatted as XML, a standard way for communication between two incompatible system. And this message is sent via HTTP, so that they can reach to any machine on the internet without being blocked by firewall.

Examples for Web Service

Weather Reporting: You can use Weather Reporting web service to display weather information in your personal website.

Stock Quote: You can display latest update of Share market with Stock Quote on your web site.

News Headline: You can display latest news update by using News Headline Web Service in your website.

In summary you can any use any web service which is available to use. You can make your own web service and let others use it. Example you can make Free SMS Sending Service with footer with your advertisement, so whosoever use this service indirectly advertise your company... You can apply your ideas in N no. of ways to take advantage of it.

Frequently used word with web services

What is SOAP?

SOAP (simple object access protocol) is a remote function calls that invokes method and execute them on Remote machine and translate the object communication into XML format. In short, SOAP are way by which method calls are translate into XML format and sent via HTTP.

What is WSDL? 

WSDL stands for Web Service Description Language, a standard by which a web service can tell clients what messages it accepts and which results it will return.

WSDL contains every detail regarding using web service and Method and Properties provided by web service and URLs from which those methods can be accessed and Data Types used.

What is UDDI?

UDDI allows you to find web services by connecting to a directory.

What is Discovery or .Disco Files?

Discovery files are used to group common services together on a web server. Discovery files .Disco and .VsDisco are XML based files that contains link in the form of URLs to resources that provides discovery information for a web service. Disco File contains URL for the WSDL, URL for the documentation and URL to which SOAP messages should be sent.

Before start creating web service first create one table in your database and give name UserInformationin my code I am using same name and enter some dummy data for our testing purpose

Column Name	Data Type	Allow Nulls
UserId	Int(Set Identity=true)	No
UserName	Varchar(50)	Yes
FirstName	Varchar(50)	Yes
LastName	Varchar(50)	Yes
Location	Varchar(50)	Yes

Now we will see how to create new web service application in asp.net

Open visual studio ---> Select File ---> New ---> Web Site ---> select ASP.NET Web Service

Now our new web service ready our webservice website like this

Now open your Service.cs file in web service website to write the code to get the user details from database

Before writing the WebMethod in Service.cs first add following namespaces

using System.Xml; using System.Configuration; using System.Data; using System.Data.SqlClient;

After adding namespaces write the following method GetUserDetails in Service.cs page

[WebMethod] public XmlElement GetUserDetails(string userName) { SqlConnection con = newSqlConnection(ConfigurationManager.ConnectionStrings["dbconnection"].ToString()); con.Open(); SqlCommand cmd = new SqlCommand("select * from UserInformation where UserName like @userName+'%'", con); cmd.Parameters.AddWithValue("@userName", userName); cmd.ExecuteNonQuery(); SqlDataAdapter da = new SqlDataAdapter(cmd); // Create an instance of DataSet. DataSet ds = new DataSet(); da.Fill(ds); con.Close(); // Return the DataSet as an XmlElement. XmlDataDocument xmldata = new XmlDataDocument(ds); XmlElement xmlElement = xmldata.DocumentElement; return xmlElement; }

Here we need to remember one point that is adding [WebMethod] before method definition because we need to access web method pulically otherwise it’s not possible to access method publically. If you observe above code I converted dataset to XmlElement t because sometimes we will get error like return type dataset invalid type it must be either an IListSource, IEnumerable, or IDataSource to avoid this error I converted dataset to XmlElement.

Here we need to set the database connection in web.config because here I am getting database connection from web.config

<connectionStrings> <add name="dbconnection" connectionString="Data Source=SureshDasari;Integrated Security=true;Initial Catalog=MySampleDB"/> </connectionStrings>

Now run your web service it would be like this

Our web service is working fine now we need to know how we can use webservice in our application? Before to know about using web service in application first Deploy your webservice application in your local system if you want to know how to deploy application in your local system check this link deploy application in local system

How to Use Web service in web application?

By using this webservice we can get the user details based on username. For that first create one new web application

Open visual studio ---> Select File ---> New ---> Web Site ---> select ASP.NET Web Site

After creation of new website right click on solution explorer and choose “Add web reference” that would be like this

After select Add Web reference option one window will open like this 

Now enter your locally deployed web service link and click Go button after that your web service will found and window will looks like this

Now click on Add Reference button web service will add successfully. Now open your Default.aspx page and design like this

<html xmlns="http://www.w3.org/1999/xhtml"> <head runat="server"> <title>Getting Data from WebService</title> </head> <body> <form id="form1" runat="server"> <div> <table> <tr> <td> <b>Enter UserName:</b> </td> <td> <asp:TextBox ID="txtUserName" runat="server"></asp:TextBox> </td> <td> <asp:Button ID="btnSubmit" runat="server" Text="Submit" onclick="btnSubmit_Click" /> </td> </tr> </table> </div> <div> <asp:GridView ID="gvUserDetails" runat="server" EmptyDataText="No Record Found"> <RowStyle BackColor="#EFF3FB" /> <FooterStyle BackColor="#507CD1" Font-Bold="True" ForeColor="White" /> <PagerStyle BackColor="#2461BF" ForeColor="White" HorizontalAlign="Center" /> <HeaderStyle BackColor="#507CD1" Font-Bold="True" ForeColor="White" /> <AlternatingRowStyle BackColor="White" /> </asp:GridView> </div> </form> </body> </html>

Now in code behind add following namespaces

using System.Data; using System.Xml;

After adding namespaces write the following code in code behind

protected void Page_Load(object sender, EventArgs e) { if(!IsPostBack) { BindUserDetails(""); } } protected void BindUserDetails(string userName) { localhost.Service objUserDetails = new localhost.Service(); DataSet dsresult = new DataSet(); XmlElement exelement = objUserDetails.GetUserDetails(userName); if(exelement!=null) { XmlNodeReader nodereader = new XmlNodeReader(exelement); dsresult.ReadXml(nodereader, XmlReadMode.Auto); gvUserDetails.DataSource = dsresult; gvUserDetails.DataBind(); } else { gvUserDetails.DataSource = null; gvUserDetails.DataBind();    } } protected void btnSubmit_Click(object sender, EventArgs e) { BindUserDetails(txtUserName.Text); }

Now run your application and check output