C # The foreach statement cyclically retrieves objects

C # The foreach statement cyclically retrieves objects
1. Get the value of the drop-down box

Foreach (listitem item in dropdownlistdepartment. Items)
{}
2.
Foreach (datarow DR in DT. Rows)
{}
3 foreach (gridviewrow row in GV. Rows)
{}
4 arraylist selectedusers = getselected ();
Foreach (string loginname in selectedusers)
{
}
5 hashtable
Hashtable queryitems = new hashtable ();
Foreach (dictionaryentry item in queryitems)
{
}

Datarow DR = dB. getdatarow (SQL );
For (INT I = 0; I <dr. itemarray. length; I ++)
{