Connecting a C# Array to a WPF Control 2-way

I would suggest using ObservableCollections instead of ArrayLists, as they will provide notifications when they change, and your UI would update accordingly.

Then, you could do this :

Account:

public struct Account
{
  public string AccountNo { get; set; }
  public double Amount { get; set; }
}

Person:

public class Person : INotifyPropertyChanged
{
  public Person()
  {
     Accounts.Add(new Account { AccountNo = "12345", Amount = 79.50 });
     Accounts.Add(new Account { AccountNo = "23456", Amount = 19.40 });
     Accounts.Add(new Account { AccountNo = "34567", Amount = 5.60 });
     Accounts.Add(new Account { AccountNo = "45678", Amount = 109.14 });
  }

  private string _name;
  public string Name
  {
     get { return _name; }
     set
     {
        if (_name == value)
           return;
        _name = value;
        if (PropertyChanged != null)
           PropertyChanged(this, new PropertyChangedEventArgs("Name"));
     }
  }

  private List<Account> _accounts = new List<Account>();
  public List<Account> Accounts
  {
     get { return _accounts; }
     set
     {
        if (_accounts != value)
        {
           _accounts = value;
           if (PropertyChanged != null)
              PropertyChanged(this, new PropertyChangedEventArgs("Accounts"));
        }
     }
  }

  public event PropertyChangedEventHandler PropertyChanged;

}

With some sort of ListBox ItemTemplating, like

<ListBox ItemsSource="{Binding People}">
        <ListBox.ItemTemplate>
            <DataTemplate>
                <StackPanel Orientation="Vertical">
                    <TextBlock Text="{Binding Name}" />
                    <ListBox ItemsSource="{Binding Accounts}">
                        <ListBox.ItemTemplate>
                            <DataTemplate>
                                <StackPanel Orientation="Horizontal">
                                    <TextBlock Text="{Binding AccountNo}" />
                                    <TextBlock Text="{Binding Amount}" />
                                </StackPanel>
                            </DataTemplate>
                        </ListBox.ItemTemplate>
                    </ListBox>
                    <TextBlock Text="{Binding Amount}" />
                </StackPanel>
            </DataTemplate>
        </ListBox.ItemTemplate>
    </ListBox>

Wpf runs best on bindings. For bindings to work, you need the underlying properties to be notifiable. So try adding a wrapper (ModelView?) around your struct properties and provide notifiable properties.