Ответ:

//C# 7.3, .NET Framework 4.7.2

namespace Brainly

{

using System;

using System.Collections.Generic;

using System.Linq;

public class Program

{

 private static Random r = new Random();

 public static void Main()

 {

  var Xi = RandomArray(10, () => r.Next(-10, 10));

  Xi.Println();

  var notZeroCount = Xi.Count(item => item != 0);

  var replaced = Xi.Replace(item => item != 0, 1);

  notZeroCount.Println();

  replaced.Println();

 }

 private static T[] RandomArray<T>(int count, Func<T> next)

 {

  var temp = new T[count];

  for(var i = 0; i < count; i++)

   temp[i] = next();

  return temp;

 }

}

public static class Extensions

{

 public static IEnumerable<T> Replace<T>(this IEnumerable<T> source, Func<T, bool> selector, T newValue)

 {

  foreach (var item in source)

  {

   if (selector(item))

    yield return newValue;

   else  

    yield return item;

  }

 }

 public static int Count<T>(this IEnumerable<T> source, Func<T, bool> selector)

 {

  var count = 0;

  foreach (var item in source)

   if (selector(item)) count++;

  return count;

 }

 public static void Println<T>(this T[] source)

 {

  foreach (var item in source)

   Console.Write(item.ToString() + " ");

 }

 public static void Println<T>(this IEnumerable<T> source)

 {

  source.ToArray().Println();

 }

 public static void Println<T>(this T source)

 {

  Console.WriteLine(source);

 }

}

}