ListBox.ObjectCollection.Add(Object) ListBox.ObjectCollection.Add(Object) ListBox.ObjectCollection.Add(Object) ListBox.ObjectCollection.Add(Object) Method

定義

將項目加入至 ListBox 的項目清單。Adds an item to the list of items for a ListBox.

public:
 int Add(System::Object ^ item);
public int Add (object item);
member this.Add : obj -> int
Public Function Add (item As Object) As Integer

參數

item
Object Object Object Object

物件,表示要加入至集合中的項目。An object representing the item to add to the collection.

傳回

集合中項目之以零起始的索引;如果已呼叫 BeginUpdate() 則為 -1。The zero-based index of the item in the collection, or -1 if BeginUpdate() has been called.

實作

例外狀況

空間不足,無法將新項目加入至清單中。There is insufficient space available to add the new item to the list.

範例

下列程式碼範例示範如何建立ListBox控制項,以在資料行中顯示多個專案,並可在控制項清單中選取一個以上的專案。The following code example demonstrates how to create a ListBox control that displays multiple items in columns and can have more than one item selected in the control's list. 範例ListBox的程式碼會Add使用ListBox.ObjectCollection類別的方法,將50專案新增至,然後使用SetSelected方法從清單中選取三個專案。The code for the example adds 50 items to the ListBox using the Add method of the ListBox.ObjectCollection class and then selects three items from the list using the SetSelected method. 然後,程式ListBox.SelectedObjectCollection代碼會顯示集合中的值( SelectedItems透過屬性) SelectedIndicesListBox.SelectedIndexCollection (透過屬性)。The code then displays values from the ListBox.SelectedObjectCollection collection (through the SelectedItems property) and the ListBox.SelectedIndexCollection (through the SelectedIndices property). 這個範例會要求程式碼位於,並從Form呼叫。This example requires that the code is located in and called from a Form.

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 );
   
   #if defined(DEBUG)
   // 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 ] );
   #endif
}

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());             
}

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

備註

如果的ListBox true屬性設定為,則會依字母順序將專案插入清單中。 SortedIf the Sorted property of the ListBox is set to true, the item is inserted into the list alphabetically. 否則,專案會插入至清單的結尾。Otherwise, the item is inserted at the end of the list. 若要將專案插入清單方塊中的特定位置,請使用Insert方法。To insert an item into the list box at a specific position, use the Insert method. 若要在單一作業中將一組專案新增至清單方塊,請使用AddRange方法。To add a set of items to the list box in a single operation, use the AddRange method. 如果Add您想要使用方法將大量專案新增至清單,請BeginUpdate使用ListBoxEndUpdate方法,以避免每次將專案新增至清單時重新繪製,直到將所有專案新增至清單為止。If you want to use the Add method to add a large number of items to the list, use the BeginUpdate and EndUpdate methods to prevent the ListBox from repainting each time an item is added to the list until all items are added to the list. 將專案加入至ListBox時,先排序專案,然後再加入新專案,會更有效率。When adding items to a ListBox, it is more efficient to sort the items first and then add new items.

當物件新增至集合時, ListBox第一個會檢查DisplayMember ListControl類別的屬性是否具有取得專案文字時,指定要參考之物件的成員名稱。When an object is added to the collection, the ListBox first checks to see if the DisplayMember property of the ListControl class has the name of a member from the object specified to reference when obtaining the item text. 如果屬性未指定成員ListBox ,則會呼叫ToString物件的方法,以取得要顯示在清單中的文字。 DisplayMemberIf the DisplayMember property does not have a member specified, the ListBox then calls the ToString method of the object to obtain the text to display in the list.

適用於