Who have the answer of chapter11 q1.
thank U very much.

I'm a relative newbie when it comes to C# but here's what I came up with for the answer to the first question in the Exercise section of Chapter 11. I've included the code to two .CS files, one that creates the collection and one that uses it. Hope this helps. Let me know if anyone has any issues with this or has a better idea for handling the question.

Here's the collection stuff -

using System;
using System.Collections;

namespace Ch11People
{
    public class Person
    {
        private string name;
        private int age;

        public string Name
        {
            get
            {
                return name;
            }
            set
            {
                name = value;
            }
        }

        public int Age
        {
            get
            {
                return age;
            }
            set
            {
                age = value;
            }
        }

        // This is the constructor for the Person class

        public Person(string newName, int newAge)
        {
            name = newName;
            age = newAge;
        }
    }

    // This defines the Collection of persons, namely People.

    public class People : CollectionBase
    {
        public void Add(Person newPerson)
        {
            List.Add(newPerson);
        }


        // This is the 'normal' indexer, using an integer to get at the collection.

        public Person this[int person_index]
        {
            get
            {
                return (Person)List[person_index];
            }
        }

        // This is the string indexer.

        public Person this[ string name ]
        {
            get
            {
                int i;

                for (i = 0;i < List.Count;i++)
                {
                    Person tmp_person = (Person) List[i];

                    if ( tmp_person.Name == name )
                    {
                        i = List.Count;
                    }
                }

                if (i == List.Count)
                    return (Person)List[i];
                else
                    return(new Person("John Doe", 999));
            }
        }
    }
}


and here's the client that uses it.

using System;
using Ch11People;

namespace PeopleClient
{
    /// <summary>
    /// Summary description for Class1.
    /// </summary>
    class Class1
    {
        /// <summary>
        /// The main entry point for the application.
        /// </summary>
        [STAThread]
        static void Main(string[] args)
        {
            // Add some people to the collection.

            People personCollection = new People();
            personCollection.Add(new Person("Harold", 21));
            personCollection.Add(new Person("James", 35));
            personCollection.Add(new Person("William", 73));
            personCollection.Add(new Person("Harold", 75));

            // Display each person in the collection.

            foreach (Person person in personCollection)
            {
                Console.WriteLine("This is {0}, who is {1} years old.", person.Name, person.Age);
            }

            // Display using the integer indexer.

            Console.WriteLine(personCollection[0].Name);
            Console.WriteLine(personCollection[1].Name);
            Console.WriteLine(personCollection[2].Name);

            // Look for a person using the string indexer.

            int count = 0;
            for (int i = 0; i < personCollection.Count;i++)
            {
                if (personCollection[i].Name == "Harold")
                    count += 1;
            }

            Console.WriteLine("I found {0} person(s) named Harold.", count);
        }
    }
}

I realized that my code is not quite what it should be. I thought I was using the string indexer when I wasn't. Please replace in the collection code -

public Person this[ string name ]
        {
            get
            {
                int i;

                for (i = 0;i < List.Count;i++)
                {
                    Person tmp_person = (Person) List[i];

                    if ( tmp_person.Name == name )
                    {
                        i = List.Count;
                    }
                }

                if (i == List.Count)
                    return (Person)List[i];
                else
                    return(new Person("John Doe", 999));
            }
        }

with -

public Person this[ string name ]
        {
            get
            {
                int i;
                int j = 0;

                for (i = 0;i < List.Count;i++)
                {
                    Person tmp_person = (Person) List[i];

                    if ( tmp_person.Name == name )
                    {
                        j = i;
                        // I have to subtract one because the 'for' loop increments i and then checks to
                        // see if we reached the end of the loop. As a result, i will be one greater than
                        // it should be if I don't subtract one. A bit kludgy, I know.
                        i = List.Count -1;
                    }
                }

                if (i == List.Count)
                    return (Person)List[j];
                else
                    return(new Person("John Doe", 999));
            }
        }

In addition, in the client, replace this part -

// Look for a person using the string indexer.

            int count = 0;
            for (int i = 0; i < personCollection.Count;i++)
            {
                if (personCollection[i].Name == "Harold")
                    count += 1;
            }

            Console.WriteLine("I found {0} person(s) named Harold.", count);

with -

// Look for a person using the string indexer.
            string searchName = "Harold";

            Person tmp_person = personCollection[searchName];

            if (tmp_person.Name == "John Doe")
                Console.WriteLine("No person with the name {0} was found.", searchName);
            else
                Console.WriteLine("We found at least one person who is name {0}", searchName);