How to create object of class file (c#.net ) using javascript

Your C# class

public class City
{
    private string name;
    public string Name
    {
        get
        {
            return name;
        }
        set
        {
            name = value;
        }
    }

    private int population;
    public int Population
    {
        get
        {
            return population;
        }
        set
        {
            population = value;
        }
    }
}

The same class object in JavaScript

<script type = "text/javascript">
var city = {};
city.Name = "Mumbai";
city.Population = 2000;
alert(city.Name);
alert(city.Population);
</script>

You can only create a property class to send receive data you cannot access its methods. You will have to use AJAX and call web method for that

http://www.aspsnippets.com/Articles/Calling-server-side-function-from-JavaScript-in-ASP.Net.aspx