ListBox.ObjectCollection.Add 方法

项目
08/17/2007

向 ListBox 的项列表添加项。

**命名空间:**System.Windows.Forms
**程序集:**System.Windows.Forms（在 system.windows.forms.dll 中）

语法

声明
Public Function Add ( _
    item As Object _
) As Integer
用法
Dim instance As ObjectCollection
Dim item As Object
Dim returnValue As Integer

returnValue = instance.Add(item)

public int Add (
    Object item
)

public:
int Add (
    Object^ item
)

public int Add (
    Object item
)

public function Add (
    item : Object
) : int

参数

item
一个对象，它表示要添加到集合中的项。

返回值

集合中项的从零开始的索引。

异常

异常类型	条件
SystemException	没有足够的空间来向列表中添加新项。

备注

如果 ListBox 的 Sorted 属性设置为 true，则该项将按字母顺序插入到列表中。否则，在列表的结尾处插入项。若要将项插入列表框的特定位置，请使用 Insert 方法。若要在一个操作中将一组项添加到列表框，请使用 AddRange 方法。如果要使用 Add 方法将大量项添加到列表中，请使用 BeginUpdate 和 EndUpdate 方法防止每次向该列表添加一个项时 ListBox 都重新绘制，直到将所有项都添加到该列表中。向 ListBox 添加项时，如果先对项进行排序，然后添加新项，则效率更高。

向集合添加对象时，ListBox 首先检查 ListControl 类的 DisplayMember 属性，检查是否指定了在获取项文本时要引用的对象中成员的名称。如果 DisplayMember 属性没有指定的成员，则 ListBox 调用对象的 ToString 方法来获取要在列表中显示的文本。

示例

下面的代码示例演示如何创建一个 ListBox 控件，该控件可在列中显示多个项，并且可在控件列表中选择多个项。该示例的代码使用 ListBox.ObjectCollection 类的 Add 方法向 ListBox 添加 50 个项，然后使用 SetSelected 方法从列表中选择三项。然后，代码显示 ListBox.SelectedObjectCollection 集合中的值（通过 SelectedItems 属性）和 ListBox.SelectedIndexCollection 中的值（通过 SelectedIndices 属性）。此示例要求代码位于 Form 中并从中调用。

Private Sub button1_Click(sender As Object, e As System.EventArgs)
    ' Create an instance of the ListBox.
    Dim listBox1 As New ListBox()
    ' Set the size and location of the ListBox.
    listBox1.Size = New System.Drawing.Size(200, 100)
    listBox1.Location = New System.Drawing.Point(10, 10)
    ' Add the ListBox to the form.
    Me.Controls.Add(listBox1)
    ' Set the ListBox to display items in multiple columns.
    listBox1.MultiColumn = True
    ' Set the selection mode to multiple and extended.
    listBox1.SelectionMode = SelectionMode.MultiExtended
    
    ' Shutdown the painting of the ListBox as items are added.
    listBox1.BeginUpdate()
    ' Loop through and add 50 items to the ListBox.
    Dim x As Integer
    For x = 1 To 50
        listBox1.Items.Add("Item " & x.ToString())
    Next x
    ' Allow the ListBox to repaint and display the new items.
    listBox1.EndUpdate()
    
    ' Select three items from the ListBox.
    listBox1.SetSelected(1, True)
    listBox1.SetSelected(3, True)
    listBox1.SetSelected(5, True)
       
    ' Display the second selected item in the ListBox to the console.
    System.Diagnostics.Debug.WriteLine(listBox1.SelectedItems(1).ToString())
    ' Display the index of the first selected item in the ListBox.
    System.Diagnostics.Debug.WriteLine(listBox1.SelectedIndices(0).ToString())
End Sub

private void button1_Click(object sender, System.EventArgs e)
{
   // Create an instance of the ListBox.
   ListBox listBox1 = new ListBox();
   // Set the size and location of the ListBox.
   listBox1.Size = new System.Drawing.Size(200, 100);
   listBox1.Location = new System.Drawing.Point(10,10);
   // Add the ListBox to the form.
   this.Controls.Add(listBox1);
   // Set the ListBox to display items in multiple columns.
   listBox1.MultiColumn = true;
   // Set the selection mode to multiple and extended.
   listBox1.SelectionMode = SelectionMode.MultiExtended;
 
   // Shutdown the painting of the ListBox as items are added.
   listBox1.BeginUpdate();
   // Loop through and add 50 items to the ListBox.
   for (int x = 1; x <= 50; x++)
   {
      listBox1.Items.Add("Item " + x.ToString());
   }
   // Allow the ListBox to repaint and display the new items.
   listBox1.EndUpdate();
      
   // Select three items from the ListBox.
   listBox1.SetSelected(1, true);
   listBox1.SetSelected(3, true);
   listBox1.SetSelected(5, true);

   // Display the second selected item in the ListBox to the console.
   System.Diagnostics.Debug.WriteLine(listBox1.SelectedItems[1].ToString());
   // Display the index of the first selected item in the ListBox.
   System.Diagnostics.Debug.WriteLine(listBox1.SelectedIndices[0].ToString());             
}

void button1_Click( Object^ /*sender*/, System::EventArgs^ /*e*/ )
{
   
   // Create an instance of the ListBox.
   ListBox^ listBox1 = gcnew ListBox;
   
   // Set the size and location of the ListBox.
   listBox1->Size = System::Drawing::Size( 200, 100 );
   listBox1->Location = System::Drawing::Point( 10, 10 );
   
   // Add the ListBox to the form.
   this->Controls->Add( listBox1 );
   
   // Set the ListBox to display items in multiple columns.
   listBox1->MultiColumn = true;
   
   // Set the selection mode to multiple and extended.
   listBox1->SelectionMode = SelectionMode::MultiExtended;
   
   // Shutdown the painting of the ListBox as items are added.
   listBox1->BeginUpdate();
   
   // Loop through and add 50 items to the ListBox.
   for ( int x = 1; x <= 50; x++ )
   {
      listBox1->Items->Add( String::Format( "Item {0}", x ) );

   }
   listBox1->EndUpdate();
   
   // Select three items from the ListBox.
   listBox1->SetSelected( 1, true );
   listBox1->SetSelected( 3, true );
   listBox1->SetSelected( 5, true );
   
   // Display the second selected item in the ListBox to the console.
   System::Diagnostics::Debug::WriteLine( listBox1->SelectedItems[ 1 ] );
   
   // Display the index of the first selected item in the ListBox.
   System::Diagnostics::Debug::WriteLine( listBox1->SelectedIndices[ 0 ] );
}

private void button1_Click(Object sender, System.EventArgs e)
{
    // Create an instance of the ListBox.
    ListBox listBox1 = new ListBox();

    // Set the size and location of the ListBox.
    listBox1.set_Size(new System.Drawing.Size(200,100));
    listBox1.set_Location(new System.Drawing.Point(10,10));

    // Add the ListBox to the form.
    this.get_Controls().Add(listBox1);

    // Set the ListBox to display items in multiple columns.
    listBox1.set_MultiColumn(true);

    // Set the selection mode to multiple and extended.
    listBox1.set_SelectionMode(SelectionMode.MultiExtended);

    // Shutdown the painting of the ListBox as items are added.
    listBox1.BeginUpdate();

    // Loop through and add 50 items to the ListBox.
    for (int x = 1; x <= 50; x++) {
        listBox1.get_Items().Add(("Item" + (new Integer(x)).ToString()));
    }

    // Allow the ListBox to repaint and display the new items.
    listBox1.EndUpdate();

    // Select three items from the ListBox.
    listBox1.SetSelected(1,true);
    listBox1.SetSelected(3,true);
    listBox1.SetSelected(5,true);

    // Display the second selected item in the ListBox to the console.
    System.Diagnostics.Debug.WriteLine
        (listBox1.get_SelectedItems().get_Item(1).ToString());

    // Display the index of the first selected item in the ListBox.
    System.Diagnostics.Debug.WriteLine((new Integer
        (listBox1.get_SelectedIndices().get_Item(0))).ToString());
} //button1_Click

private function button1_Click(sender : Object, e : System.EventArgs)
{
   // Create an instance of the ListBox.
   var listBox1 : ListBox = new ListBox();
   // Set the size and location of the ListBox.
   listBox1.Size = new System.Drawing.Size(200, 100);
   listBox1.Location = new System.Drawing.Point(10,10);
   // Add the ListBox to the form.
   this.Controls.Add(listBox1);
   // Set the ListBox to display items in multiple columns.
   listBox1.MultiColumn = true;
   // Set the selection mode to multiple and extended.
   listBox1.SelectionMode = SelectionMode.MultiExtended;
 
   // Shutdown the painting of the ListBox as items are added.
   listBox1.BeginUpdate();
   // Loop through and add 50 items to the ListBox.
   for (var x : int = 1; x <= 50; x++)
   {
      listBox1.Items.Add("Item " + x.ToString());
   }
   // Allow the ListBox to repaint and display the new items.
   listBox1.EndUpdate();
      
   // Select three items from the ListBox.
   listBox1.SetSelected(1, true);
   listBox1.SetSelected(3, true);
   listBox1.SetSelected(5, true);

   // Display the second selected item in the ListBox to the console.
   System.Diagnostics.Debug.WriteLine(listBox1.SelectedItems[1].ToString());
   // Display the index of the first selected item in the ListBox.
   System.Diagnostics.Debug.WriteLine(listBox1.SelectedIndices[0].ToString());             
}

平台

Windows 98、Windows 2000 SP4、Windows CE、Windows Millennium Edition、Windows Mobile for Pocket PC、Windows Server 2003、Windows XP Media Center Edition、Windows XP Professional x64 Edition、Windows XP SP2、Windows XP Starter Edition

.NET Framework 并不是对每个平台的所有版本都提供支持。有关受支持版本的列表，请参见系统要求。

版本信息

.NET Framework

受以下版本支持：2.0、1.1、1.0

.NET Compact Framework

受以下版本支持：2.0、1.0

请参见

参考

ListBox.ObjectCollection 类
 ListBox.ObjectCollection 成员
 System.Windows.Forms 命名空间

通过

ListBox.ObjectCollection.Add 方法

语法

参数

返回值

异常

备注

示例

平台

版本信息

.NET Framework

.NET Compact Framework

请参见

参考

其他资源