IEnumerable to string delimited with commas?

I have a DataTable that returns

IDs
,1
,2
,3
,4
,5
,100
,101

I want to convert this to single string value, i.e:

,1,2,3,4,5,100,101

How can i rewrite the following to get a single string

var _values = _tbl.AsEnumerable().Select(x => x);