在foreach循环中向前跳过C＃

Question

if I have a foreach loop that takes a whole bunch of addresses and loops through them, is there a way I could skip the first 500 entries,

something like:

foreach(var row in addresses)
{
  string strAddr = row.ADDRESS + "," + row.CITY + "," + row.ST;
  System.Threading.Thread.Skip(500)
}

I know skip doesn't exist but is there anything I can use that would do the same thing?

Answer 1

You can use a method with a meaningful name:

foreach(var row in addresses.Skip(500))
{
    // ...
}

You need to add using System.Linq; since it's a LINQ extension method.

If the type of addresses doesn't implement the generic IEnumerable<T> interface you could use Cast<T> . For example (presuming the type is Address ):

foreach(var row in addresses.Cast<Address>().Skip(500))
{
    // ...
}

Answer 2

You can use the Skip extension method:

foreach(var row in addresses.Skip(500))
{
    string strAddr = row.ADDRESS + "," + row.CITY + "," + row.ST;
}

Or, if addresses is just an array or list:

for (int i = 500 ; i < addresses.Count ; i++) // assuming addresses is a List<T>
{
    var row = addresses[i];
    string strAddr = row.ADDRESS + "," + row.CITY + "," + row.ST;
}

Answer 3

Use the Enumerator interface directly: http://msdn.microsoft.com/en-us/library/system.collections.ienumerator(v=vs.110).aspx

var enumerator = addresses.GetEnumerator();
for (var i = 0; i < 300 && enumerator.MoveNext(); i++);

Answer 4

A feasible and fast solution would be to use LINQ Skip method to iterate over a subset of the collection starting from the 500th element of the collection.

foreach (var row in addresses.Skip(500))
{
   // do your stuff...
}