//get column 1 data to a list from dataset1
var list1 = ds1.Tables[0].AsEnumerable().Select(x => x[0].ToString());
//get column 1 data to a list from dataset2
var list2 = ds2.Tables[0].AsEnumerable().Select(x => x[0].ToString());
//merge two list items
var mergedList = list1.Zip(list2, (a, b) => a + " ," + b);
// create new datatable
DataTable dt = new DataTable();
dt.Columns.Add("ColumnName", typeof(string)); // give proper column name
foreach (string item in mergedList)
{
dt.Rows.Add(item); // add each item as row
}
DataSet ds3 = new DataSet();
// add newly created table to dataset 3
ds3.Tables.Add(dt);