How to call code behind function from javascript

  function OnEmployeeChange(EmployeeList)
  {
      var empCode = EmployeeList.options[EmployeeList.selectedIndex].value
      
      EskanRyteHRMS.Personal_Transfer.SetEmployeeProperties(empCode, OnEmployeeChange_callback)
     // Personal_Transfer.SetEmployeeProperties(empCode, OnEmployeeChange_callback)
}

function OnEmployeeChange_callback(response)
{
    if (response != null)
    {
        var DataRow = response.value;
        
         var dlOldLocation = document.getElementById("<%=dlOldLocation.ClientID%>");
          var dlLocation = document.getElementById("<%=dlLocation.ClientID%>");             
        dlOldLocation.value = dlLocation.value = DataRow[4];

          var dlOldDepartment = document.getElementById("<%=dlOldDepartment.ClientID%>");
          var dlDepartment = document.getElementById("<%=dlDepartment.ClientID%>");
                                 
        dlDepartment.value = dlOldDepartment.value = DataRow[3];

        var dlOldReportTo = document.getElementById("<%=dlOldReportTo.ClientID%>");
        var dlReportTo = document.getElementById("<%=dlReportTo.ClientID%>");
        
        dlOldReportTo.value = dlReportTo.value = DataRow[2];

        var dlOldDivision = document.getElementById("<%=dlOldDivision.ClientID%>");
        var dlDivision = document.getElementById("<%=dlDivision.ClientID%>");
        
        dlOldDivision.value = dlDivision.value = DataRow[1];

          var dlOldDesignation = document.getElementById("<%=dlOldDesignation.ClientID%>");
        var dlDesignation = document.getElementById("<%=dlDesignation.ClientID%>");
        
        dlOldDesignation.value = dlDesignation.value = DataRow[0];
    }
}

<ajaxpro.ajaxmethod()>
Public Function SetEmployeeProperties(ByVal EmployeeCode As String) As System.Data.DataRow
    Dim result As Data.DataRow = Nothing
    Dim dtTable As Data.DataTable = New DataAccessLayer.DataConnection(GB.PropertyManager(Session).ActiveConnectionString).ExecuteToDataSet("select DesigCode,DivCode,ReportTo,DeptCode,LocationID,JobGrade,Rank from employee_mst Where EmpCode = " + EmployeeCode).Tables(0)
    If (dtTable.Rows.Count > 0) Then
        result = dtTable.Rows(0)
    End If
    Return result
End Function