c# how to get last time in foreach statement? [duplicate]

This question already has answers here: 开发者_运维问答 Closed 10 years ago.

Possible Duplicate:

Foreach loop, determine which is the last iteration of the loop

foreach (DataRowView row in orderedTable.DefaultView)
{
    if(lasttime) do-something;
}

orderedtable is a datatable

does anyone know how to find out whether we are on the last foreach iteration? please keep in mind that i do have duplicates in orderedtable

---

The correct method that works in all cases is to use the IEnumerator<T> directly:

using (var enumerator = orderedTable.DefaultView.GetEnumerator())
{
    if (enumerator.MoveNext())
    {
        bool isLast;
        do
        {
            var current = enumerator.Current;
            isLast = !enumerator.MoveNext();
            //Do stuff here
        } while (!isLast);
    }
}

This method works even if your collection doesn't have a Count property, and even if it does, this method will be more efficient if the Count property is slow.

---

The foreach construct does not know such a thing, since it applies equally to unbounded lists. It just has no way of knowing what is a last item.

You can iterate the manual way as well, though:

for (int i = 0; i < orderedTable.DefaultView.Count; i++) {
    DataRowView row = orderedTable.DefaultView[i];
    if (i == orderedTable.DefaulView.Count - 1) {
        // dosomething
    }
}

---

An alternative approach which I don't think anyone posted. This works well if you don't know the count ahead of time.

DataRowView lastRow;
foreach (DataRowView row in orderedTable.DefaultView)
{
    // Do something...

    lastRow = row;
}

if (lastRow != null)
{
  // Do something with last row
}

---

You will have to use a regular for loop if you want to have different behavior on the last item.

for (int i = 0; i < orderedTable.DefaultView.Count; i++)
{
    //do stuff
    if (i == orderedTable.DefaultView.Count - 1)
    {
        //do additional special stuff
    }
}

It's worth noting that "the other Skeet" has an implementation for a "smart enumerable" which supports a Last property. See the article here: http://msmvps.com/blogs/jon_skeet/archive/2007/07/27/smart-enumerations.aspx

With this you could write something like this (I might get the details wrong, haven't tried it out myself):

foreach (SmartEnumerable<DataRowView> item in new SmartEnumerable<DataRowView>(orderedTable.DefaultView))
{
    DataRowView row = item.Value;
    if(item.IsLast)
    {
       ///do special stuff
    }
}

---

Instead of using foreach get the IEnumerator. If MoveNext returns null the previous was the last one.

for would work too of course.

---

You could possibly do something like the following:

foreach (DataRowView row in orderedTable.DefaultView)
{
    if(row == orderedTable.DefaultView.Last()) do-something;
}

But its pretty inefficient.

---

If you're concerned in keeping track of your iteration, why not use a for instead or a foreach? Then you can simply do the following:

for(int i = 0; i<orderedTable.DefaultView.Count-1;i++)
{
   if(i==orderedTable.DefaultView.Count-1)
   {
      // Last Row
   }
}

---

The code you have posted is identical to:

if (orderedTable.DefaultView.Rows.Count > 0)
    do-something;

If that does not do what you want, you will have to explain what lastTime does.

---

If I understand your question, does this help?

int lastrow = 0;
foreach (DataRow row in table.Rows) // Loop over the rows.
{
    lastrow++;
    // Do Something
    if (lastrow == (table.Rows.Count - 1))
    {
        // Do something else
    }
}