BindingSource.AllowNew 属性

  • 参考

定义

命名空间:
System.Windows.Forms
程序集:
System.Windows.Forms.dll

获取或设置一个值，该值指示是否可以使用 AddNew() 方法向列表中添加项。

public:
 virtual property bool AllowNew { bool get(); void set(bool value); };
public virtual bool AllowNew { get; set; }
member this.AllowNew : bool with get, set
Public Overridable Property AllowNew As Boolean

属性值

Boolean

如果可以使用 AddNew() 向列表中添加项，则为 true；否则为 false。

例外

InvalidOperationException

当 List 属性表示的基础列表具有固定大小或为只读时，此属性设置为 true。

MissingMethodException

当基础列表类型没有无参数构造函数时，该属性设置为 true，并且不会处理 AddingNew 事件。

示例

下面的代码示例演示如何使用 AllowNew 组件的 属性 BindingSource 来允许用户将新项添加到 BindingSource 组件的基础列表。 将此属性设置为 true 会导致绑定 DataGridView 控件显示新记录的行。

Form1()
{
   // Set up the form.
   this->Size = System::Drawing::Size( 800, 800 );
   this->Load += gcnew EventHandler( this, &Form1::Form1_Load );
   
   // Set up the RadioButton controls.
   this->allRadioBtn->Text = L"All";
   this->allRadioBtn->Checked = true;
   this->allRadioBtn->CheckedChanged += gcnew EventHandler(
      this, &Form1::allRadioBtn_CheckedChanged );
   this->allRadioBtn->Dock = DockStyle::Top;
   this->currentRadioBtn->Text = L"Current";
   this->currentRadioBtn->CheckedChanged += gcnew EventHandler(
      this, &Form1::currentRadioBtn_CheckedChanged );
   this->currentRadioBtn->Dock = DockStyle::Top;
   this->noneRadioBtn->Text = L"None";
   this->noneRadioBtn->CheckedChanged += gcnew EventHandler(
      this, &Form1::noneRadioBtn_CheckedChanged );
   this->noneRadioBtn->Dock = DockStyle::Top;
   this->buttonPanel->Controls->Add( this->allRadioBtn );
   this->buttonPanel->Controls->Add( this->currentRadioBtn );
   this->buttonPanel->Controls->Add( this->noneRadioBtn );
   this->buttonPanel->Dock = DockStyle::Bottom;
   this->Controls->Add( this->buttonPanel );
   
   // Set up the DataGridView control.
   this->customersDataGridView->AllowUserToAddRows = true;
   this->customersDataGridView->Dock = DockStyle::Fill;
   this->Controls->Add( customersDataGridView );
   
   // Add the StatusBar control to the form.
   this->Controls->Add( status );
   
   // Allow the user to add new items.
   this->customersBindingSource->AllowNew = true;
   
   // Attach an event handler for the AddingNew event.
   this->customersBindingSource->AddingNew +=
      gcnew AddingNewEventHandler(
         this, &Form1::customersBindingSource_AddingNew );
   
   // Attach an eventhandler for the ListChanged event.
   this->customersBindingSource->ListChanged +=
      gcnew ListChangedEventHandler(
         this, &Form1::customersBindingSource_ListChanged );
   
   // Set the initial value of the ItemChangedEventMode property
   // to report all ListChanged events.
   this->customersBindingSource->ItemChangedEventMode = 
     ItemChangedEventMode::All;
   
   // Attach the BindingSource to the DataGridView.
   this->customersDataGridView->DataSource =
      this->customersBindingSource;
}

public Form1()
{
    // Set up the form.
    this.Size = new Size(800, 800);
    this.Load += new EventHandler(Form1_Load);

    // Set up the DataGridView control.
    this.customersDataGridView.AllowUserToAddRows = true;
    this.customersDataGridView.Dock = DockStyle.Fill;
    this.Controls.Add(customersDataGridView);

    // Add the StatusBar control to the form.
    this.Controls.Add(status);

    // Allow the user to add new items.
    this.customersBindingSource.AllowNew = true;

    // Attach an event handler for the AddingNew event.
    this.customersBindingSource.AddingNew +=
        new AddingNewEventHandler(customersBindingSource_AddingNew);

    // Attach an eventhandler for the ListChanged event.
    this.customersBindingSource.ListChanged +=
        new ListChangedEventHandler(customersBindingSource_ListChanged);

    // Attach the BindingSource to the DataGridView.
    this.customersDataGridView.DataSource =
        this.customersBindingSource;
}

Public Sub New() 
    ' Set up the form.
    Me.Size = New Size(800, 800)
    AddHandler Me.Load, AddressOf Form1_Load
    
    ' Set up the DataGridView control.
    Me.customersDataGridView.AllowUserToAddRows = True
    Me.customersDataGridView.Dock = DockStyle.Fill
    Me.Controls.Add(customersDataGridView)
    
    ' Add the StatusBar control to the form.
    Me.Controls.Add(status)
    
    ' Allow the user to add new items.
    Me.customersBindingSource.AllowNew = True
    
    ' Attach the BindingSource to the DataGridView.
    Me.customersDataGridView.DataSource = Me.customersBindingSource

End Sub

注解

属性的 AllowNew 默认值取决于基础数据源类型。 如果基础列表实现 IBindingList 接口，则此属性将委托给基础列表。 否则，如果基础列表具有以下任何特征，则此属性将返回 false ：

注意

设置此属性的值后，getter 不再引用对基础列表的调用。 相反，它只是返回之前设置的值， ResetAllowNew 直到调用 方法。

设置此属性将ListChanged引发设置为 ListChangedType.Reset的事件ListChangedEventArgs.ListChangedType。

如果将 属性设置为 AllowNewtrue ，而基础列表类型没有无参数构造函数，则必须处理 AddingNew 事件并创建适当的类型。

适用于

另请参阅