Is there any method to fill the combobox in winforms with all country names and another combobox with cities of the selected country? OR may be just the list of countries in combobox

Question

I wonder if there is already a build procedure in C# for making a combobox or list box that has names of all countries and when a country is selected another combobox is filled with the cities of that country??

Or someone can suggest me what to do!!

Answer 1

There is no such procedure. I suggest that you make a combo box and populate it with countries, and another one with cities when a country was selected. That way, you have full control over what countries and cities appear in your combo boxes.

Answer 2

Sure there is a procedure. You could start with a simple data structure:

public class Country
{
  public string Name { get; set; }
  public IList<City> Cities { get; set; }

  public Country()
  {
    Cities = new List<City>();
  }
}

public class City { public string Name { get; set; } }

Then, instantiate this structure, e.g. into a property of your form...

Countries =
  new List<Country>
    {
      new Country
        {
          Name = "Germany",
          Cities =
            {
              new City {Name = "Berlin"},
              new City {Name = "Hamburg"}
            }
        },
      new Country
        {
          Name = "England",
          Cities =
            {
              new City {Name = "London"},
              new City {Name = "Birmingham"}
            }
        }
    };

In your form, instantiate two Binding Sources (BS):

• The first BS binds to the Countries property.
• The second BS binds to the first (DataSource = firstBS) and its DataMember should be "Cities".

Now you need two dropdowns:

• 1st: DataSource = first BS, DisplayMember = "Name"
• 2nd: DataSource = second BS, DisplayMember = "Name"

and you should be pretty much done.