MVP Winforms和文本框组合框的值

Question

我有一个下拉框，其数据源为一个包含对象（客户）及其属性（姓名、地址等）的列表。 当我选择下拉框中的某个项目时，我想将信息（地址、邮政编码等）传递到表单上的一些文本框中。 在我的一层测试应用程序中，这个功能是正常工作的。 但是，我正在处理的主要应用程序是基于MVP（带有我的自定义设置）。我面临的问题是类型转换。由于视图不知道我的模型，我不应该使用（客户）代码行：string address = ((Customers)comboBox1.SelectedItem).CustomerAddress;

private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
{
    //getCustomers((int)comboBox1.SelectedValue);
    //txtAddress.Text =Convert.ToString( comboBox1.SelectedValue);
    Customers p = (Customers)comboBox1.SelectedItem;
    string s = comboBox1.SelectedItem.ToString();
    string address = ((Customers)comboBox1.SelectedItem).CustomerAddress;
    txtAddress1.Text = address;
}

private void Form3_Load(object sender, EventArgs e)
{
    using (var emp = new EmployerEFEntities())
    {
        var query = from customers in emp.Customers
                    select customers;

        comboBox1.DisplayMember = "CustomerName";
        comboBox1.ValueMember = "CustomerID";
        comboBox1.DataSource = query.ToList();
    }
}

我是一个能够翻译文本的助手。

我已经花费了几天时间研究这个问题，但一直未能成功。我希望有人能给我正确的方向。

真实应用程序的代码：

视图：

private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
{
    txtName.Text = comboBox1.SelectedValue.ToString();
}

private void CustomerView_Load(object sender, EventArgs e)
{
    comboBox1.DataSource = customerPresenter.getCustomers();
    comboBox1.DisplayMember = "CustomerName";
    comboBox1.ValueMember = "CustomerId";
}

演示者：

public List<tbl_customer> getCustomers()
{
    using (var customers = new DBCrownfishEntities())
    {
        var customer = from c in customers.tbl_customer
                       select c;

        return customer.ToList();
    }
}

- Kevin

Answer 1

这只是一种实现的方式。您的MVP模式可能会有所不同。 在此实现中，View知道Presenter。有关MVP的更多信息，请参见这里 您可以将Presenter用作客户端的包装器：

public interface IPresenter
{
    void Init();
    void SetSelectedCustomer(int customerId);
    IEnumerable GetCustomers();
    string FirstName { get; set; }
    string LastName { get; set; }
    string Address { get; set; }
}

Presenter必须实现INotifyPropertyChanged接口（并在属性的setter方法中调用OnPropertyChanged方法）。

public class Presenter : IPresenter, INotifyPropertyChanged
{
    private readonly Repository _repository;
    private string _firstName;
    private string _lastName;
    private string _address;
    private Customer _currentCustomer;

    public Presenter(Repository repository)
    {
        _repository = repository;
    }

    public string FirstName
    {
        get { return _firstName; }
        set
        {
            if (_firstName == value) return;
            _firstName = value;
            OnPropertyChanged();
        }
    }

    public string LastName
    {
        get { return _lastName; }
        set
        {
            if (_lastName == value) return;
            _lastName = value;
            OnPropertyChanged();
        }
    }

    public string Address
    {
        get { return _address; }
        set
        {
            if (_address == value) return;
            _address = value;
            OnPropertyChanged();
        }
    }

    public IEnumerable GetCustomers()
    {
        return _repository.GetAllCustomers();
    }

    public void Init()
    {
        var result = _repository.GetAllCustomers();
        SetSelectedCustomer(result[0].Id);
    }

    public void SetSelectedCustomer(int customerId)
    {
        var customer = _repository.GetCustomerById(customerId);
        FirstName = customer.FirstName;
        LastName = customer.LastName;
        Address = customer.Address;
    }

    public event PropertyChangedEventHandler PropertyChanged;

    protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }
}

这是视图的样子：

public partial class Form1 : Form
{
    private IPresenter _presenter;
    private bool _initialized;

    public Form1(IPresenter presenter)
    {
        InitializeComponent();           
        _presenter = presenter;
        _presenter.Init();
        SetComboBoxData(_presenter.GetCustomers());
        _initialized = true;
    }

    public void SetComboBoxData(IEnumerable data)
    {
        comboBox1.DataSource = data;
        comboBox1.ValueMember = "Id";
        comboBox1.DisplayMember = "FirstName";
    }

    private void comboBox1_SelectedIndexChanged(object sender, System.EventArgs e)
    {
        if (!_initialized) return;
        _presenter.SetSelectedCustomer((int)comboBox1.SelectedValue);
    }

    private void Form1_Load(object sender, System.EventArgs e)
    {
        textBox1.DataBindings.Add(new Binding("Text", _presenter, nameof(_presenter.FirstName)));
        textBox2.DataBindings.Add(new Binding("Text", _presenter, nameof(_presenter.LastName)));
        textBox3.DataBindings.Add(new Binding("Text", _presenter, nameof(_presenter.Address)));
    }
}

您可以在选定的客户下拉列表的SelectedIndexChanged事件中将所选的CustomerId设置为Presenter:

_presenter.SetSelectedCustomer((int)comboBox1.SelectedValue);

在您的Presenter中的SetSelectedCustomer方法（或者SelectedCustomerChanged事件的EventHandler）会选择具有给定CustomerId的客户，并设置其FirstName、LastName和Address属性:

public void SetSelectedCustomer(int customerId)
{
    var customer = _repository.GetCustomerById(customerId);
    FirstName = customer.FirstName;
    LastName = customer.LastName;
    Address = customer.Address;
}

您应该在Form_Load中为TextBoxes进行绑定：

textBox1.DataBindings.Add(new Binding("Text", _presenter, nameof(_presenter.FirstName)));
textBox2.DataBindings.Add(new Binding("Text", _presenter, nameof(_presenter.LastName)));
textBox3.DataBindings.Add(new Binding("Text", _presenter, nameof(_presenter.Address)));

- Andy

Answer 2

如果您绝对不允许视图访问表示数据表行的域对象（这取决于它们的重量，在某些情况下可能是可以接受的），您可能需要考虑使用DTO。请查看this，了解相关考虑事项和一种实现方法。请注意底部提到的Automapper。这是一个很棒的工具。

编辑：我刚意识到您对Winforms解决方案感兴趣，而不是ASP.NET的解决方案。尽管上面的链接涉及ASP.NET，但对于Winforms应用程序，思路是相同的。

- RobC