Q:

Convert int to timespan in SQL script (SQL Server)

The query is done in an sql script. 
My Problem : 
I need to pass the data in a model as json.
Thats why i need to convert it to a timespan in the sql script.
--TEMP
DECLARE @startDate DATETIME
SET @startDate = '01-09-2016'

DECLARE @endDate DATETIME
SET @endDate = '03-10-2017'
--END

SELECT
Firstname,
Lastname,
COUNT(Token.Id) as Tokens,
**CONVERT(time, SUM(DATEDIFF(ss, Token.ArrivalTime, Token.CompletionTime)), 57) as [Time]**
FROM Employee
INNER JOIN Token ON Token.Employee_Id = Employee.Id
WHERE AssignmentTime >= @startDate and AssignmentTime <= @endDate
and Status = 2
GROUP BY Firstname, Lastname
ORDER BY Tokens DESC
FOR JSON PATH

The error is: 
The explicit conversion from data type int to time is not allowed

What the output should look like : "Hans", "Muster", 5, 400
Thanks in advance!

A:

At the end it wasn't that hard. I didnt parse the int to timespan in the sql query. I got a error in every variation, no matter what I tried.
Thats my solution:
DATEDIFF(ss, Token.ArrivalTime, Token.CompletionTime) as TimeInSeconds

In the ViewModel which is getting passed in the controller, I parse it:
    public int TimeInSeconds { get; set; }
    public TimeSpan Time
    {
        get { return TimeSpan.FromSeconds(TimeInSeconds); }
    }

