Column data in to single row with comma seperated

Below SQl statement is used for convert single column data in a single row.

declare @testdata varchar(8000)
set @testdata=''

select @testdata=@testdata+NAME+', ' from User where ID in('1','2','3','4','5')
print @testdata

select substring(@testdata,0,len(@testdata))


In above User is a table
NAME is column of user which data will be manuplate in row
ID is column of user
Actual data format was:

After query the data format will be: