Displaying A String Returned From A Web Service In An AJAX Call

Hi all,

My web method in my web service successfully retrieved the total row count from a database. If the return value is zero the variable "is_unique" is set to "true" else if the return value is 1 or more, it is set to "false". Then the variable "is_unique" is returned. The following are my code snippets.

//--------------- Web Service Code Snippet

[WebMethod]
public string function GetTotal(string firstname, string lastname)  
{

 if(firstname.length==0){return"Please enter first name";}; 

 if(lastname.length==0){return"Please enter last name";}; 

 string is_unique = "false"; 

 //---- ADO.NET Code goes here
 //---- More ADO.Net code 
 //---- More ADO.NET code 
 //---- More ADO.NET code
 //---- More ADO.NET code

 con.Open(); 
 cmd.ExecuteNonQuery();

 int count = Convert.ToInt32(outputParam.Value);
 if (count == 0) { is_unique = "true"; } 
 else if(count>=1) { is_unique = "false"; } 
 con.Close(); 
 return is_unique;
}

//--------------AJAX function on the frontend 

function IsUnique() {
var jdata = {firstname: "Test", lastname: "Test"};$.ajax({
                url: "http://localhost:21577/MyService.asmx/GetTotal",              
                data:jdata,
                method: "Post",                
                dataType: "xml",
                success: function (data) {                 
                    alert(data.value);
                }
            });
}

The problem I am having is that when I try to retrieve data from the web service in the AJAX call on the frontend using "data.value", I get "Undefined". Please help me resolve this problem.