错误95'System.Array'不包含'FindIndex'的定义

Question

I am converting my existing Windows Phone 8 app to WP 7.1. However I've encountered an error

'System.Array' does not contain a definition for 'FindIndex'

in this line. What am I missing?

index = Array.FindIndex(AnswerLevelArr, s => s.Contains(CurrentFileName));

Answer 1

Array.FindIndex Method (T[], Predicate) is not supported in Windows Phone 7.1.

Version Information

Windows Phone OS
Supported in: 8.0

Instead, you may use Linq (make sure that you add using System.Linq; to the top of your file):

index = AnswerLevelArr
    .Select((i, position) => new { Item = i, IndexOf = position })
    .First(s => s.Item.Contains(CurrentFileName)).IndexOf;

or:

int index=0;
var result = AnswerLevelArr.SkipWhile((s, ind) =>
{
    if (!s.Contains(CurrentFileName))
    {
        index++;
        return false;
    }
    else
    {
        return true;
    }
}).First();

Answer 2

according to msdn

public static int FindIndex<T>(
    T[] array,
    Predicate<T> match
)

http://msdn.microsoft.com/en-us/library/03y7c6xy.aspx

you need to include the type?

EDIT: index = Array.FindIndex<T>(AnswerLevelArr, s => s.Contains(CurrentFileName));

EDIT2: Left above up for history but is wrong after further inspection...

If you wanted a find index similar to your method you could provide an override

int FindIndex(string s)
{
    int size = this.length;
    for(int i = 0; i < size; i++)
    {
    if(this[i] = s)
        return i;
     }
     return -1;
}

Answer 3

From Array.FindIndex<T> Method (T[], Predicate<T>)

Version Information
Windows Phone OS
Supported in: 8.0

It is looks like this method not supported in Windows Phone 7.1