I am trying to retrieve a list of IDs from a list of object[]
. Here is my code:
private static List<int> getReceivedIds(object[] objectList)
{
var received = new List<int>();
foreach (object[] b in objectList)
{
if (b != null)
{
received.Add(int.Parse((b[0].ToString())));
}
}
return received;
}
I am looking for a performance optimised solution for this code.
I changed the code to this:
private static List<int> getReceivedIds2(object[] objectList)
{
var received = new List<int>();
foreach (object[] b in objectList)
{
if (b != null)
{
received.Add((int)b[0]);
}
}
return received;
}
Also I compared the LINQ query and foreach
statement performance and here is the result: Performance test results
The test shows that the foreach
statement is 6 times faster than LINQ.
Anybody can improve the performance of this code?
Here is the code for my test:
class Program
{
static void Main(string[] args)
{
for (int test = 0; test < 100; test++)
{
object[] objectList = new object[1000];
Random rnd = new Random();
for (int i = 0; i < 1000; i++)
{
objectList[i] = new object[] { rnd.Next(1, 10000), rnd.Next(1, 10000), rnd.Next(1, 10000), rnd.Next(1, 10000), rnd.Next(1, 10000), rnd.Next(1, 10000), rnd.Next(1, 10000), rnd.Next(1, 10000), rnd.Next(1, 10000), rnd.Next(1, 10000), rnd.Next(1, 10000), rnd.Next(1, 10000), rnd.Next(1, 10000), rnd.Next(1, 10000), rnd.Next(1, 10000), rnd.Next(1, 10000), rnd.Next(1, 10000), rnd.Next(1, 10000), rnd.Next(1, 10000), rnd.Next(1, 10000), rnd.Next(1, 10000) };
}
Stopwatch stopWatch = new Stopwatch();
stopWatch.Start();
for (int i = 1; i < 100000; i++)
{
getReceivedIds(objectList);
}
stopWatch.Stop();
var t1 = stopWatch.Elapsed.TotalMilliseconds;
stopWatch.Restart();
for (int i = 1; i < 100000; i++)
{
getReceivedIds2(objectList);
}
stopWatch.Stop();
var t2 = stopWatch.Elapsed.TotalMilliseconds;
Console.WriteLine(string.Format("LINQ: {0} - ForEach: {1}", t1, t2));
}
}
private static List<int> getReceivedIds(object[] objectList)
{
List<int> received = objectList.Cast<object[]>()
.Where(b => b != null)
.Select(b => (int)b[0]) // or Convert.ToInt32(b[0])
.ToList();
return received;
}
private static List<int> getReceivedIds2(object[] objectList)
{
var received = new List<int>();
foreach (object[] b in objectList)
{
if (b != null)
{
received.Add((int)b[0]);
}
}
return received;
}
}
If the first item in the object[]
is actually an int
you don't need to parse it, you can cast it. You could use this LINQ query if you want:
List<int> received = objectList.Cast<object[]>()
.Where(b => b != null)
.Select(b => (int)b[0]) // or Convert.ToInt32(b[0])
.ToList();
try this:
int[] resultArray = Array.ConvertAll(inputArray, x => Convert.ToInt32(x));
Note : Ensure that the values are int.
For reference : msdn link for ConvertAll()
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