C＃实例化类对象并添加到列表

Question

How can I create new instance of Country which uses 3 variables firstParam, secondParam, thirdParam for its constructor and add to a List countryList?

The 3 variables are being read from .txt and split on the , Afghanistan,Kabul,30419928 Albania,Tirana,2821977

My 3 split variables firstParam, secondParam, thirdParam contain the right information. I think I am making a syntax mistake when I add to the countryList because debug mode stepping through the variables load the right info but when I try a foreach on the countryList I get the output "countries.country".

    List<Country> countryList = new List<Country>();

        foreach (string line in lines)
        {
            string[] criteria = line.Split(',');

            string firstParam = "";
            string secondParam = "";
            int thirdParam = 1;

            firstParam = criteria[0];
            secondParam = criteria[1];
            thirdParam = Convert.ToInt32(criteria[2]);

            countryList.Add(new Country(firstParam, secondParam, thirdParam));


        }

I ran out of ideas and not sure what else to try I am trying to learn more about composition but hoping someone can nudge me along. thank you.

Answer 1

If you want to choose the value for debugging, you should use this way 'Override ToString()' or 'DebuggerDisplayAttribute'.

 //DebuggerDisplayAttribute
[DebuggerDisplay("Value = {Display}")]
public class Country
{
    public string Name { get; set; }
    public string City { get; set; }    

    public string Display
    {
        get => $"{Name}, {City}";
    }

    //Override ToString()
    public override string ToString()
    {
        return $"{Name}, {City}";
    }
}

Answer 2

Try this to verify your code is working the way you want it to:

List<Country> countryList = new List<Country>();

foreach (string line in lines)
{
    string[] criteria = line.Split(',');

    countryList.Add(new Country(criteria[0],
                                criteria[1],
                                Convert.ToInt32(criteria[2]))
}

Console.WriteLine($"Countries in countryList: {countryList.Count}.");

foreach ( Country country in countryList)
{
    Console.WriteLine($"Name: {country.Name}, Capital: {country.Capital}, Population: {country.Population}.");
}

You may need to insert your own names for the fields of your Country class instead of Name, Capital, and Population.