Calling WebMethod with Multiple parameters from JavaScript Ajax

In my previous article I have explained how to call WebMethod using Ajax in JavaScript. Now, in this article I’ll show you how to call WebMethod with multiple parameters from JavaScript Ajax.

There two ways you can pass parameters (or send request with parameters) to a WebMethod from Ajax in JavaScript.

1) Passing parameters through the Ajax URL (or query strings)

2) Passing parameters through XMLHttpRequest send() method

By the way, you can call a WebMethod with multiple parameters using jQuery. Check this example.

Create WebMethod with two arguments

So, lets create the methods (in C# and VB), which will accept an Ajax request with multiple parameters.

As I said, there are two ways a WebMethod can receive multiple parameters. Therefore, I’ll create two methods: one will calculate the percentage, the other will do a simple addition.

The Web Service (C#)

using System;
using System.Web;
using System.Web.Services;

[WebService(Namespace = "http://tempuri.org/")]
[WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
[System.Web.Script.Services.ScriptService]
public class WebService : System.Web.Services.WebService {

    [WebMethod()]
    public double percentage(double leftOperand, double rightOperand)
    {
        var perc = (leftOperand / rightOperand) * 100;
        return Math.Round(perc);
    }

    [WebMethod]
    public int calculate_sum()
    {
        int val1 = int.Parse(HttpContext.Current.Request.QueryString["l"]);
        int val2 = int.Parse(HttpContext.Current.Request.QueryString["r"]);
        return val1 + val2;
    }
}

The Web Service (Vb)

Imports System.Web
Imports System.Web.Services

<System.Web.Script.Services.ScriptService()> _
<WebService(Namespace:="http://tempuri.org/")> _
<WebServiceBinding(ConformsTo:=WsiProfiles.BasicProfile1_1)> _
<Global.Microsoft.VisualBasic.CompilerServices.DesignerGenerated()> _
Public Class WebService
    Inherits System.Web.Services.WebService

    ' Calculate the percentage.
    <WebMethod()> _
    Public Function percentage(ByVal leftOperand As Double, ByVal rightOperand As Double) As Double
        Dim perc = (leftOperand / rightOperand) * 100
        Return Math.Round(perc)
    End Function

    ' Calculate the sum of two values.
    <WebMethod()> _
    Public Function calculate_sum() As Integer
        Dim val1 As Integer = HttpContext.Current.Request.QueryString("l")
        Dim val2 As Integer = HttpContext.Current.Request.QueryString("r")
        Return val1 + val2
    End Function
End Class

The Markup

I’ll add few HTML elements like textboxes to accept inputs and a button to call the script.

<body>
    <div>
        <input type="radio" id="sum" name="t1" checked />
            <label for="sum">Calculate Sum</label>
        <input type="radio" id="percent" name="t1" />
            <label for="percent">Calculate %</label>

        <p>Enter a number <input id="val1" /></p>
        <p>Enter a number <input id="val2" /></p>

        <p><input id="bt" type="button" value="Calculate" onclick="cal()"/></p>
    </div>

    <div id='t1'></div>
</body>

The Script to call the Web Service Methods with Parameters

<script>
    let cal = () => {
        // get input values.
        let v1 = document.getElementById('val1').value;
        let v2 = document.getElementById('val2').value;

        const oXHR = new XMLHttpRequest();
        oXHR.onreadystatechange = reportStatus;

        // 1st method  (calculate the sum of two numbers)
        if (document.getElementById('sum').checked) {
            oXHR.open("POST", "WebService.asmx/calculate_sum?l=" + v1 + "&r=" + v2, true);
            oXHR.setRequestHeader("Content-Type", "application/json");
            oXHR.send();		// send request.
        }

        // 2nd method (get the percentage)
        if (document.getElementById('percent').checked) {
            oXHR.open("POST", "WebService.asmx/percentage", true);
            var params = "{ 'leftOperand': '" + v1 + "', 'rightOperand': '" + v2 + "' }";
            oXHR.setRequestHeader("Content-Type", "application/json");
            oXHR.send(params);	    // send request with parameters.
        }

        function reportStatus() {
            let ele = document.getElementById('t1');
            if (oXHR.readyState === XMLHttpRequest.DONE && oXHR.status === 200) { 
                let val = JSON.parse(this.responseText);
                if (document.getElementById('percent').checked) {
                    ele.innerHTML = 'the value is: ' + val.d + "%" ;
                }
                else ele.innerHTML = 'the value is: ' + val.d;
            }
        }
    }
</script>

I have explained about XMLHttpRequest objects in detail here.

The 1st method is making a POST request with a URL with two arguments (or parameters). The method "calculate_sum()" gets the parameters (or the values) through the QueryString() method. See the Web methods again.

The 2nd method is also making a POST request. However, the URL has no parameters or query strings. The parameters are passed using the send() method.

oXHR.send(params);

Remember, XMLHttpRequest "send()" method accepts an optional parameter. You can pass multiple parameters to a web service using the method.

You can learn more about JavaScript Ajax POST and GET methods here.

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