c# - foreach还有别的吗？

Question

我有 foreach 来显示 myquery 的结果，它在结果不为空时起作用。我想知道 foreach 还有其他吗？当 myquery 的结果为空时采取行动？

var rs = from cs in db.CsCustomers
                      from ai in db.ArInvoices
                      where cs.CustomerID == ai.CustomerID &&
                      ai.Kategori != null
                      orderby cs.Unit
                      select new
                      {
                          cs.CustomerID,
                          cs.Unit,
                          cs.Name
                      };

foreach (var r in rs)
{
     c = new TableCell();
     c.Text = r.CustomerID;
     c.RowSpan = jk;
     tr.Cells.Add(c);

     c = new TableCell();
     c.Text = r.Unit;
     c.RowSpan = jk;
     tr.Cells.Add(c);

     c = new TableCell();
     c.Text = r.Name;
     c.RowSpan = jk;
     tr.Cells.Add(c);

}

Answer 1

为什么不先检查 -

if(rs == null)
{}
else
{
  foreach.....
}