Remove First and last comma from string in SQl

Remove First and last comma from string in SQl

 declare @Str nvarchar(max)=',kandy,'

  if(right(rtrim(@Str),1) = ',')

begin

        set @Str= substring(rtrim(@Str),1,len(rtrim(@Str))-1)

 end

if(left(ltrim(@Str),1) = ',')

begin

       set @Str=Substring(@Str, 2, (len(@Str)))

end

select @Str