How to use session state (ASP.Net Web Services)

To use the session object in ASP.NET in web services, there are two things that need to be done.

1. The WebService class needs to inherit the System.Web.Services.WebService class

2. The EnableSession attribute value in WebMethod should be set to true

Looking at our CalculatorWebService class, we can see that it has inherited the System.Web.Services.WebService class. However, we need the EnableSession property value to be set to true.

In this article, we will try to use a session object in a GridView as shown below to display the latest calculation results.

In order to achieve this The purpose is to first think of the following, modify the Add method of the CalculatorWebService class.

[WebMethod(EnableSession = true)]
        public int Add(int firstNumber, int secondNumber)
        {
            List<string> calculations;

            if (Session["CALCULATIONS"] == null)
            {
                calculations = new List<string>();
            }
            else
            {
                calculations = (List<string>)Session["CALCULATIONS"];
            }
            
            string strTransaction = firstNumber.ToString() + " + " 
                + secondNumber.ToString() 
                + " = " + (firstNumber + secondNumber).ToString();
            calculations.Add(strTransaction);
            Session["CALCULATIONS"] = calculations;

            return firstNumber + secondNumber;
        }

Then introduce another public method to return all calculation results. Use the WebMethod feature to Modify this method and set the EnableSession attribute to true.

[WebMethod(EnableSession = true)]
        public List<string> GetCalculations()
        {
            if (Session["CALCULATIONS"] == null)
            {
                List<string> calculations = new List<string>();
                calculations.Add("You have not performed any calculations");
                return calculations;
            }
            else
            {
                return (List<string>)Session["CALCULATIONS"];
            }
        }

Now we can build our solution and view our Web service in the browser .

The Web service will list two methods - Add and GetCalculations.

Click the Add method. Let's enter two numbers, say 20 and 30, and click the Invoke button, we will get the result 50.

Let’s do another calculation, such as 30 and 70. Then click the Invoke button and we will get the result as 100.

## Now let’s go back and test our GetCalculation method. Then click on the Invoke method, which will now display all the calculations we did before. They will be returned in the form of a

stringarray.

In this way, our Web service operates as expected. Now let's try using these methods in our web application. To do this, in Webform1.aspx, let us drag a GridView

control into it.

<tr>
    <td>
        <asp:GridView ID="gvCalculations" runat="server">
        </asp:GridView>
    </td>
</tr>

Before the code after the file modification, we The proxy class needs to be updated. To do this, go to CalculatorService and select Update Service Reference.

After that, in the btnAdd_Click event code segment, add the following lines of code.

gvCalculations.DataSource = client.GetCalculations();
            gvCalculations.DataBind();

            gvCalculations.HeaderRow.Cells[0].Text = "Recent Calculations";

Build our solution and view this web window in a browser.

Let’s go ahead and add two numbers, say 20 and 30. And we will see that although we have performed a calculation, the message "You have not performed any calculations" will still be displayed.

This is basically because the web application is not sending the same SessionId as the web service. To do this, set allowCookie in the web.config file to true.

Now let’s run the web again window and add some numbers. Now we can see that it works as expected.

Therefore, here are a few points to think about deeply:

• If the Web service is modified, the client application's proxy class must be updated. To do this, right-click on the service under the Service Reference folder and select the Update Service Reference item.

• Set the allowCookies attribute to true to allow the client application to accept cookies returned from the ASMX Web service and copy them to all future requests initiated by the Web service. This ensures that the connection between the client and the Web service is The same Session is maintained.

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