Fill List<int> with default values?
C#ListC# Problem Overview
> Possible Duplicate:
> Auto-Initializing C# Lists
I have a list of integers that has a certain capacity that I would like to automatically fill when declared.
List<int> x = new List<int>(10);
Is there an easier way to fill this list with 10 ints that have the default value for an int rather than looping through and adding the items?
C# Solutions
Solution 1 - C#
Well, you can ask LINQ to do the looping for you:
List<int> x = Enumerable.Repeat(value, count).ToList();
It's unclear whether by "default value" you mean 0 or a custom default value.
You can make this slightly more efficient (in execution time; it's worse in memory) by creating an array:
List<int> x = new List<int>(new int[count]);
That will do a block copy from the array into the list, which will probably be more efficient than the looping required by ToList
.
Solution 2 - C#
int defaultValue = 0;
return Enumerable.Repeat(defaultValue, 10).ToList();
Solution 3 - C#
if you have a fixed length list and you want all the elements to have the default value, then maybe you should just use an array:
int[] x = new int[10];
Alternatively this may be a good place for a custom extension method:
public static void Fill<T>(this ICollection<T> lst, int num)
{
Fill(lst, default(T), num);
}
public static void Fill<T>(this ICollection<T> lst, T val, int num)
{
lst.Clear();
for(int i = 0; i < num; i++)
lst.Add(val);
}
and then you can even add a special overload for the List class to fill up to the capacity:
public static void Fill<T>(this List<T> lst, T val)
{
Fill(lst, val, lst.Capacity);
}
public static void Fill<T>(this List<T> lst)
{
Fill(lst, default(T), lst.Capacity);
}
Then you can just say:
List<int> x = new List(10).Fill();
Solution 4 - C#
Yes
int[] arr = new int[10];
List<int> list = new List<int>(arr);
Solution 5 - C#
var count = 10;
var list = new List<int>(new int[count]);
ADD
Here is generic method to get the list with default values:
public static List<T> GetListFilledWithDefaulValues<T>(int count)
{
if (count < 0)
throw new ArgumentException("Count of elements cannot be less than zero", "count");
return new List<T>(new T[count]);
}