What is the best way to find something in a list? I know LINQ has some nice tricks, but let's also get suggestions for C# 2.0. Lets get the best refactorings for this common code pattern.
Currently I use code like this:
// mObjList is a List<MyObject>
MyObject match = null;
foreach (MyObject mo in mObjList)
{
if (Criteria(mo))
{
match = mo;
break;
}
}
or
// mObjList is a List<MyObject>
bool foundIt = false;
foreach (MyObject mo in mObjList)
{
if (Criteria(mo))
{
foundIt = true;
break;
}
}
Put the code in a method and you save a temporary and a break
(and you recycle code, as a bonus):
T Find<T>(IEnumerable<T> items, Predicate<T> p) {
foreach (T item in items)
if (p(item))
return item;
return null;
}
… but of course this method already exists anyway for Lists, even in .NET 2.0.
Using a Lambda expression:
List<MyObject> list = new List<MyObject>();
// populate the list with objects..
return list.Find(o => o.Id == myCriteria);
Evidently the performance hit of anonymous delegates is pretty significant.
Test code:
static void Main(string[] args)
{
for (int kk = 0; kk < 10; kk++)
{
List<int> tmp = new List<int>();
for (int i = 0; i < 100; i++)
tmp.Add(i);
int sum = 0;
long start = DateTime.Now.Ticks;
for (int i = 0; i < 1000000; i++)
sum += tmp.Find(delegate(int x) { return x == 3; });
Console.WriteLine("Anonymous delegates: " + (DateTime.Now.Ticks - start));
start = DateTime.Now.Ticks;
sum = 0;
for (int i = 0; i < 1000000; i++)
{
int match = 0;
for (int j = 0; j < tmp.Count; j++)
{
if (tmp[j] == 3)
{
match = tmp[j];
break;
}
}
sum += match;
}
Console.WriteLine("Classic C++ Style: " + (DateTime.Now.Ticks - start));
Console.WriteLine();
}
}
Results:
Anonymous delegates: 710000
Classic C++ Style: 340000
Anonymous delegates: 630000
Classic C++ Style: 320000
Anonymous delegates: 630000
Classic C++ Style: 330000
Anonymous delegates: 630000
Classic C++ Style: 320000
Anonymous delegates: 610000
Classic C++ Style: 340000
Anonymous delegates: 630000
Classic C++ Style: 330000
Anonymous delegates: 650000
Classic C++ Style: 330000
Anonymous delegates: 620000
Classic C++ Style: 330000
Anonymous delegates: 620000
Classic C++ Style: 340000
Anonymous delegates: 620000
Classic C++ Style: 400000
In every case, using anonymous delegates is about 100% slower than the other way.
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