using System;

using System.Linq;

using System.Collections.Generic;

​

public class Program

{

    public static void Main()

    {

        try

        {

            PerformCallAndHandleExceptions(() => ThrowingEnumerable(true));

            Console.WriteLine("The call didn't throw. This is bad.");

        }

        catch

        {

            Console.WriteLine("The call threw before enumaration. The fix worked!");

        }

    }

​

    // Try commenting this method and it will fail.

    private static IEnumerable<TResult> PerformCallAndHandleExceptions<TResult>(Func<IEnumerable<TResult>> performCall)

    {

        return PerformCallAndHandleExceptions<IEnumerable<TResult>>(() => performCall().PeekFirst());

    }

​

    private static TResult PerformCallAndHandleExceptions<TResult>(Func<TResult> performCall)

    {

        try

        {

            return performCall();

        }

        catch (Exception)

        {

            // Handle exceptions... 

            throw;

        }

    }

​

    private static IEnumerable<bool> ThrowingEnumerable(bool shouldThrow)

    {

        if (shouldThrow)

        {

            throw new Exception("Flute!");

        }

​

        yield return true;

    }

}

​

public static class EnumerableExtension

{

    public static IEnumerable<T> PeekFirst<T>(this IEnumerable<T> e)

    {

        return e.ToList(); // We have a real "PeekFirst" that does something smarter here.

    }

}