问题
Is there a reason why I can\'t do the following:
foreach (var Item in DataTable.Rows) {
rather than having to do
foreach (DataRow Item in DataTable.Rows) {
I would have thought this was possible, like it is on other datatypes. For example:
foreach (var Employee in Staff) { // string[] Staff etc...
When I try the first foreach loop, I get the the error CS0021: Cannot apply indexing with [] to an expression of type \'object\'.
Why can\'t the compiler figure out that .Rows returns a collections of DataRows?
回答1:
Rows effectively returns IEnumerable (DataRowCollection), so the compiler can only pick object as the type for var. Use Rows.Cast<DataRow> if you want to use var.
Cast is defined on Enumerable, so you have to include System.Linq.
回答2:
Brian is absolutely right about the reason for this, but there's a simpler way of avoiding it: use DataTableExtensions.AsEnumerable():
foreach (var row in DataTable.AsEnumerable())
{
...
}
来源：https://stackoverflow.com/questions/2325777/why-cant-i-do-foreach-var-item-in-datatable-rows