Is there an equivalent to F#'s List.map function in C#? i.e. apply a function to each element in the list and return a new list containing the results.
Something like:
public static IEnumerable<TResult> Map<TSource, TResult>(this IEnumerable<TSource> source, Func<TSource, TResult> funky)
{
foreach (TSource element in source)
yield return funky.Invoke(element);
}
Is there already a built in way or should I just write the custom extension?
3 Answers
That is LINQ's Select - i.e.
var newSequence = originalSequence.Select(x => {translation});
or
var newSequence = from x in originalSequence
select {translation};
ConvertAll is the built-in function:
public List<TOutput> ConvertAll<TOutput>(
Converter<T, TOutput> converter
)
Available since .NET version 2.0.
MSDN code example:
using System;
using System.Drawing;
using System.Collections.Generic;
public class Example
{
public static void Main()
{
List<PointF> lpf = new List<PointF>();
lpf.Add(new PointF(27.8F, 32.62F));
lpf.Add(new PointF(99.3F, 147.273F));
lpf.Add(new PointF(7.5F, 1412.2F));
Console.WriteLine();
foreach( PointF p in lpf )
{
Console.WriteLine(p);
}
List<Point> lp = lpf.ConvertAll(
new Converter<PointF, Point>(PointFToPoint));
Console.WriteLine();
foreach( Point p in lp )
{
Console.WriteLine(p);
}
}
public static Point PointFToPoint(PointF pf)
{
return new Point(((int) pf.X), ((int) pf.Y));
}
}
/* This code example produces the following output:
{X=27.8, Y=32.62}
{X=99.3, Y=147.273}
{X=7.5, Y=1412.2}
{X=27,Y=32}
{X=99,Y=147}
{X=7,Y=1412}
*/
To simplify what @codeape said:
List<string> result = ListWithAnyObjects.ConvertAll<string>(obj => obj.ToString());
