Combine two or more Web Methods in one in ASP.Net

Here I have created sample that will help you out.

HTML

<div>
    <script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.7.2/jquery.min.js"></script>
    <script type="text/javascript">
        function addData() {
            debugger;
            var Customers = new Array();
            var Employeeid = 0;
            var Emplyeename = 'Name';
            $('[id*=trans_gridview]').find('tr:has(td)').each(function () {
                var Customer = {};
                Customer.ID = $(this).find("td:nth-child(2)").html();
                Customer.ProductName = $(this).find("td:nth-child(4)").html();
                Customer.Amount = $(this).find("td:nth-child(5)").html();
                Customer.Rate = $(this).find("td:nth-child(6)").html();
                Customers.push(Customer);
            });
            $.ajax({
                type: 'POST',
                url: "Default.aspx/SaveGridViewRowData",
                data: '{Customers: ' + JSON.stringify(Customers) + ',EmployeeId:"' + Employeeid + '",EmployeeName:"' + Emplyeename + '"}',
                contentType: "application/json; charset=utf-8",
                dataType: "json",
                success: function (response) {
                    if (response.d) {
                        alert('Data Saved Sucessfully');
                        return false;
                    }
                }
            });
        };
    </script>
    <asp:Button Text="Save" runat="server" OnClientClick="addData()" />
</div>

Code

[WebMethod]
public static bool SaveGridViewRowData(List<Customerdata> Customers, int EmployeeId, string EmployeeName)
{
    InsertEmployeedata(EmployeeId, EmployeeName);
    // Write Here Code to insert Grid Data
    return true;
}

[WebMethod]
public static void InsertEmployeedata(int EmployeeId, string EmployeeName)
{
    if (EmployeeId > 0 && !string.IsNullOrEmpty(EmployeeName))
    {
        // Write Here code two insert 
    }
}

CustomerData Class

public class Customerdata
{
    public int ID { get; set; }
    public string ProductName { get; set; }
    public decimal Amount { get; set; }
    public decimal Rate { get; set; }
}

I hope this will help you out.