使用用戶控件的表單不會返回值

Question

我在寫用戶控件。我希望它在用戶雙擊客戶時返回客戶編號。我似乎無法得到它的工作。顯示用戶控件，雙擊時，數據顯示在消息框中，但似乎無法使其更新主窗體上的值。

每當我試圖返回值加入到FindCustomerControl_ItemHasBeenSelected，我得到一個錯誤。這就像它掛在用戶控件中，我不能讓它返回值。到目前爲止，這是我所：

在我的主窗口：

public partial class TestForm : Form 
{ 
    public TestForm() 
    { 
     InitializeComponent(); 
    } 

    private void button1_Click(object sender, EventArgs e) 
    { 
     // one close button on the form 
     Close(); 
    } 


    private void ShowSelectFromListWidget() 
    { 
     // show the user control 
     var uc = new FindCustomerControl(); 
     uc.ItemHasBeenSelected += uc_ItemHasBeenSelected; 

     MakeUserControlPrimaryWindow(uc); 
    } 

    void uc_ItemHasBeenSelected(object sender, 
         FindCustomerControl.SelectedItemEventArgs e) 
    { 
     // once it has been selected, change a label on the screen to show the customer number 
     var value = e.SelectedChoice; 
     lblCustomer.Text = value; 
    } 

} 

在我的用戶控制：

public partial class FindCustomerControl : UserControl 
{ 
    public class SelectedItemEventArgs : EventArgs 
    { public string SelectedChoice { get; set; } } 

    public event EventHandler<SelectedItemEventArgs> ItemHasBeenSelected; 


    public FindCustomerControl() 
     { InitializeComponent();} 


    DataTable dt = new DataTable(); 
    public void btnFind_Click(object sender, EventArgs e) 
    { var dt = GetData(); 
     dataGridView1.DataSource = dt; } 

    //Query database 
    public DataTable GetData() 
    { 
     UtilitiesClass ru = new UtilitiesClass(); 
     string connectionString = ru.getConnectionString(); 

     DataTable dt = new DataTable(); 

     SqlConnection myConnection = new SqlConnection(connectionString); 
     myConnection.Open(); 
     SqlCommand cmd = new SqlCommand("FindCustomer", myConnection); 
     cmd.Parameters.AddWithValue("@customer", txtCustomer.Text.Trim()); 
     cmd.CommandType = CommandType.StoredProcedure; 
     SqlDataAdapter ta = new SqlDataAdapter(cmd); 
     ta.Fill(dt); 
     myConnection.Close(); 
     return (dt); 
    } 

    private void dataGridView1_CellDoubleClick(object sender, DataGridViewCellEventArgs e) 
    { 
     var handler = ItemHasBeenSelected; 
     string choice = dataGridView1[0, e.RowIndex].Value.ToString(); 
     // this shows it 
     MessageBox.Show("Chosen: " + e.SelectedChoice); 
     if (handler != null) handler(this, new SelectedItemEventArgs { SelectedChoice = choice }); 
     // I WOULD LIKE TO RETURN A VALUE HERE 
    } 


} 

它好像這應該是很常見，但儘管我的研究和調試時間，我一直無法提出解決方案。我知道，uc.ItemHasBeenSelected + = uc_ItemHasBeenSelected;在TestForm似乎並沒有得到執行，因爲我在那裏放置了一個斷點。

Answer 1

用戶類沒有任何問題。它工作正常。問題在於TestForm需要在沒有FindCustomerControl的情況下啓動，並在程序中實例化控件。它將值返回到標籤或其他需要的地方。非常感謝布拉德·雷姆和這個職位：Return value from usercontrol after user action

public partial class TestForm : Form 
    { 
    public TestForm() 
    { 
     InitializeComponent(); 
     ShowSelectFromListWidget(); 
    } 

    private void button1_Click(object sender, EventArgs e) 
    { 
     Close(); 
    } 


    private void ShowSelectFromListWidget() 
    { 
     var uc = new FindCustomerControl(); 
     uc.ItemHasBeenSelected += uc_ItemHasBeenSelected; 
     this.MakeUserControlPrimaryWindow(uc); 
    } 

    void uc_ItemHasBeenSelected(object sender, FindCustomerControl.SelectedItemEventArgs e) 
    { 
     var value = e.SelectedChoice; 
     lblCustomer.Text = value; 
     lblMerchant.Focus(); 

     //ClosePrimaryUserControl(); 
    } 

    private void MakeUserControlPrimaryWindow(UserControl uc) 
    { 
     // my example just puts in in a panel, but for you 
     // put your special code here to handle your user control management 
     panel1.Controls.Add(uc); 
    } 


    private void ClosePrimaryUserControl() 
    { 
     // put your special code here to handle your user control management 
     panel1.Controls.Clear(); 
    } 

}

Answer 2

我的理解我想你可以使用應用現有資源，在那裏你可以保存任何你希望的值 - 在UWP它是這樣的：

Application.Current.Resources["Name"] = customerNumber 

然後你可以將此值轉換爲所需的類型：

(int)Application.Current.Resources["Name"] 

現在你可以在任何你想要的地方使用這個值。

希望不是以任何方式幫助。