ListBox.ObjectCollection 类
定义
重要
一些信息与预发行产品相关,相应产品在发行之前可能会进行重大修改。 对于此处提供的信息,Microsoft 不作任何明示或暗示的担保。
表示 ListBox 中项的集合。
public: ref class ListBox::ObjectCollection : System::Collections::IList
[System.ComponentModel.ListBindable(false)]
public class ListBox.ObjectCollection : System.Collections.IList
[<System.ComponentModel.ListBindable(false)>]
type ListBox.ObjectCollection = class
interface IList
interface ICollection
interface IEnumerable
Public Class ListBox.ObjectCollection
Implements IList
- 继承
-
ListBox.ObjectCollection
- 派生
- 属性
- 实现
示例
下面的代码示例通过将 属性设置为 DrawModeOwnerDrawVariable
值并处理 DrawItem 和 MeasureItem 事件来演示所有者绘制ListBox。 它还演示如何设置 BorderStyle 和 ScrollAlwaysVisible 属性以及使用 AddRange 方法。
若要运行此示例,请将其粘贴到导入命名空间和命名空间的 System.Drawing 空窗体中 System.Windows.Forms 。 从窗体的构造函数或Load
方法调用InitializeOwnerDrawnListBox
。
internal:
System::Windows::Forms::ListBox^ ListBox1;
private:
void InitializeOwnerDrawnListBox()
{
this->ListBox1 = gcnew System::Windows::Forms::ListBox;
// Set the location and size.
ListBox1->Location = Point(20,20);
ListBox1->Size = System::Drawing::Size( 240, 240 );
// Populate the ListBox.ObjectCollection property
// with several strings, using the AddRange method.
array<Object^>^temp0 = {"System.Windows.Forms","System.Drawing","System.Xml","System.Net","System.Runtime.Remoting","System.Web"};
this->ListBox1->Items->AddRange( temp0 );
// Turn off the scrollbar.
ListBox1->ScrollAlwaysVisible = false;
// Set the border style to a single, flat border.
ListBox1->BorderStyle = BorderStyle::FixedSingle;
// Set the DrawMode property to the OwnerDrawVariable value.
// This means the MeasureItem and DrawItem events must be
// handled.
ListBox1->DrawMode = DrawMode::OwnerDrawVariable;
ListBox1->MeasureItem += gcnew MeasureItemEventHandler( this, &Form1::ListBox1_MeasureItem );
ListBox1->DrawItem += gcnew DrawItemEventHandler( this, &Form1::ListBox1_DrawItem );
this->Controls->Add( this->ListBox1 );
}
// Handle the DrawItem event for an owner-drawn ListBox.
void ListBox1_DrawItem( Object^ /*sender*/, DrawItemEventArgs^ e )
{
// If the item is the selected item, then draw the rectangle
// filled in blue. The item is selected when a bitwise And
// of the State property and the DrawItemState.Selected
// property is true.
if ( (e->State & DrawItemState::Selected) == DrawItemState::Selected )
{
e->Graphics->FillRectangle( Brushes::CornflowerBlue, e->Bounds );
}
else
{
// Otherwise, draw the rectangle filled in beige.
e->Graphics->FillRectangle( Brushes::Beige, e->Bounds );
}
// Draw a rectangle in blue around each item.
e->Graphics->DrawRectangle( Pens::Blue, e->Bounds );
// Draw the text in the item.
e->Graphics->DrawString( ListBox1->Items[ e->Index ]->ToString(), this->Font, Brushes::Black, (float)e->Bounds.X, (float)e->Bounds.Y );
// Draw the focus rectangle around the selected item.
e->DrawFocusRectangle();
}
// Handle the MeasureItem event for an owner-drawn ListBox.
void ListBox1_MeasureItem( Object^ sender, MeasureItemEventArgs^ e )
{
// Cast the sender object back to ListBox type.
ListBox^ theListBox = dynamic_cast<ListBox^>(sender);
// Get the string contained in each item.
String^ itemString = dynamic_cast<String^>(theListBox->Items[ e->Index ]);
// Split the string at the " . " character.
array<Char>^temp1 = {'.'};
array<String^>^resultStrings = itemString->Split( temp1 );
// If the string contains more than one period, increase the
// height by ten pixels; otherwise, increase the height by
// five pixels.
if ( resultStrings->Length > 2 )
{
e->ItemHeight += 10;
}
else
{
e->ItemHeight += 5;
}
}
internal System.Windows.Forms.ListBox ListBox1;
private void InitializeOwnerDrawnListBox()
{
this.ListBox1 = new System.Windows.Forms.ListBox();
// Set the location and size.
ListBox1.Location = new Point(20, 20);
ListBox1.Size = new Size(240, 240);
// Populate the ListBox.ObjectCollection property
// with several strings, using the AddRange method.
this.ListBox1.Items.AddRange(new object[]{"System.Windows.Forms",
"System.Drawing", "System.Xml", "System.Net", "System.Runtime.Remoting",
"System.Web"});
// Turn off the scrollbar.
ListBox1.ScrollAlwaysVisible = false;
// Set the border style to a single, flat border.
ListBox1.BorderStyle = BorderStyle.FixedSingle;
// Set the DrawMode property to the OwnerDrawVariable value.
// This means the MeasureItem and DrawItem events must be
// handled.
ListBox1.DrawMode = DrawMode.OwnerDrawVariable;
ListBox1.MeasureItem +=
new MeasureItemEventHandler(ListBox1_MeasureItem);
ListBox1.DrawItem += new DrawItemEventHandler(ListBox1_DrawItem);
this.Controls.Add(this.ListBox1);
}
// Handle the DrawItem event for an owner-drawn ListBox.
private void ListBox1_DrawItem(object sender, DrawItemEventArgs e)
{
// If the item is the selected item, then draw the rectangle
// filled in blue. The item is selected when a bitwise And
// of the State property and the DrawItemState.Selected
// property is true.
if ((e.State & DrawItemState.Selected) == DrawItemState.Selected)
{
e.Graphics.FillRectangle(Brushes.CornflowerBlue, e.Bounds);
}
else
{
// Otherwise, draw the rectangle filled in beige.
e.Graphics.FillRectangle(Brushes.Beige, e.Bounds);
}
// Draw a rectangle in blue around each item.
e.Graphics.DrawRectangle(Pens.Blue, e.Bounds);
// Draw the text in the item.
e.Graphics.DrawString(ListBox1.Items[e.Index].ToString(),
this.Font, Brushes.Black, e.Bounds.X, e.Bounds.Y);
// Draw the focus rectangle around the selected item.
e.DrawFocusRectangle();
}
// Handle the MeasureItem event for an owner-drawn ListBox.
private void ListBox1_MeasureItem(object sender,
MeasureItemEventArgs e)
{
// Cast the sender object back to ListBox type.
ListBox theListBox = (ListBox) sender;
// Get the string contained in each item.
string itemString = (string) theListBox.Items[e.Index];
// Split the string at the " . " character.
string[] resultStrings = itemString.Split('.');
// If the string contains more than one period, increase the
// height by ten pixels; otherwise, increase the height by
// five pixels.
if (resultStrings.Length>2)
{
e.ItemHeight += 10;
}
else
{
e.ItemHeight += 5;
}
}
Friend WithEvents ListBox1 As System.Windows.Forms.ListBox
Private Sub InitializeOwnerDrawnListBox()
Me.ListBox1 = New System.Windows.Forms.ListBox
' Set the location and size.
ListBox1.Location = New Point(20, 20)
ListBox1.Size = New Size(240, 240)
' Populate the ListBox.ObjectCollection property
' with several strings, using the AddRange method.
Me.ListBox1.Items.AddRange(New Object() _
{"System.Windows.Forms", "System.Drawing", "System.Xml", _
"System.Net", "System.Runtime.Remoting", "System.Web"})
' Turn off the scrollbar.
ListBox1.ScrollAlwaysVisible = False
' Set the border style to a single, flat border.
ListBox1.BorderStyle = BorderStyle.FixedSingle
' Set the DrawMode property to the OwnerDrawVariable value.
' This means the MeasureItem and DrawItem events must be
' handled.
ListBox1.DrawMode = DrawMode.OwnerDrawVariable
Me.Controls.Add(Me.ListBox1)
End Sub
' Handle the DrawItem event for an owner-drawn ListBox.
Private Sub ListBox1_DrawItem(ByVal sender As Object, _
ByVal e As DrawItemEventArgs) Handles ListBox1.DrawItem
' If the item is the selected item, then draw the rectangle filled in
' blue. The item is selected when a bitwise And of the State property
' and the DrawItemState.Selected property is true.
If (e.State And DrawItemState.Selected = DrawItemState.Selected) Then
e.Graphics.FillRectangle(Brushes.CornflowerBlue, e.Bounds)
Else
' Otherwise, draw the rectangle filled in beige.
e.Graphics.FillRectangle(Brushes.Beige, e.Bounds)
End If
' Draw a rectangle in blue around each item.
e.Graphics.DrawRectangle(Pens.Blue, e.Bounds)
' Draw the text in the item.
e.Graphics.DrawString(Me.ListBox1.Items(e.Index), Me.Font, _
Brushes.Black, e.Bounds.X, e.Bounds.Y)
' Draw the focus rectangle around the selected item.
e.DrawFocusRectangle()
End Sub
' Handle the MeasureItem event for an owner-drawn ListBox.
Private Sub ListBox1_MeasureItem(ByVal sender As Object, _
ByVal e As MeasureItemEventArgs) Handles ListBox1.MeasureItem
' Cast the sender object back to ListBox type.
Dim theListBox As ListBox = CType(sender, ListBox)
' Get the string contained in each item.
Dim itemString As String = CType(theListBox.Items(e.Index), String)
' Split the string at the " . " character.
Dim resultStrings() As String = itemString.Split(".")
' If the string contains more than one period, increase the
' height by ten pixels; otherwise, increase the height by
' five pixels.
If (resultStrings.Length > 2) Then
e.ItemHeight += 10
Else
e.ItemHeight += 5
End If
End Sub
注解
类 ListBox.ObjectCollection 存储 中显示的项 ListBox。 类中 ListBox 定义了另外两个集合,可用于确定在此集合中选择哪些项。 类 ListBox.SelectedObjectCollection 提供用于确定 在 中选择 ListBox.ObjectCollection哪些项的属性和方法, ListBox.SelectedIndexCollection 而 类使你能够确定 选择了 中的 ListBox.ObjectCollection 哪些索引。
可通过多种方式将项添加到集合中。 方法 Add 提供将单个对象添加到集合的功能。 若要向集合添加多个对象,请创建一个项数组并将其 AddRange 分配给 方法。 如果要在集合中的特定位置插入对象,可以使用 Insert 方法。 若要删除项,如果知道项在集合中的位置,RemoveRemoveAt则可以使用 方法或 方法。 使用 Clear 方法可以从集合中删除所有项,而不是使用 Remove 方法一次删除单个项。
还可以使用 DataSource 属性操作 的ListBox项。 如果使用 DataSource 属性将项添加到 ,ListBox则可以使用 Items 属性查看 中的ListBox项,但不能使用 ListBox.ObjectCollection的方法在列表中添加或删除项。
除了用于添加和删除项的方法和属性外, ListBox.ObjectCollection 还提供用于查找集合中的项的方法。 使用 Contains 方法可以确定对象是否为集合的成员。 知道项位于集合中后,可以使用 IndexOf 方法确定项在集合中的位置。
构造函数
属性
Count |
获取集合中的项数。 |
IsReadOnly |
获取一个值,该值指示集合是否为只读。 |
Item[Int32] |
获取或设置集合中指定索引处的项。 |
方法
Add(Object) |
向 ListBox 的项列表添加项。 |
AddRange(ListBox+ObjectCollection) |
将现有 ListBox.ObjectCollection 的项添加到 ListBox 中项的列表中。 |
AddRange(Object[]) |
向 ListBox 的项列表添加项的数组。 |
Clear() |
从集合中移除所有项。 |
Contains(Object) |
确定指定的项是否位于集合内。 |
CopyTo(Object[], Int32) |
将整个集合复制到现有对象的数组中,从该数组内的指定位置开始复制。 |
Equals(Object) |
确定指定对象是否等于当前对象。 (继承自 Object) |
GetEnumerator() |
返回一个枚举数,将使用该枚举数循环访问项集合。 |
GetHashCode() |
作为默认哈希函数。 (继承自 Object) |
GetType() |
获取当前实例的 Type。 (继承自 Object) |
IndexOf(Object) |
返回指定的项在集合中的索引。 |
Insert(Int32, Object) |
将一个项插入列表框中指定的索引处。 |
MemberwiseClone() |
创建当前 Object 的浅表副本。 (继承自 Object) |
Remove(Object) |
从集合中删除指定的对象。 |
RemoveAt(Int32) |
移除集合中指定索引处的项。 |
ToString() |
返回表示当前对象的字符串。 (继承自 Object) |
显式接口实现
ICollection.CopyTo(Array, Int32) |
此 API 支持产品基础结构,不能在代码中直接使用。 从特定的数组索引开始,将集合的元素复制到数组中。 |
ICollection.IsSynchronized |
有关此成员的说明,请参见 IsSynchronized。 |
ICollection.SyncRoot |
有关此成员的说明,请参见 SyncRoot。 |
IList.Add(Object) |
此 API 支持产品基础结构,不能在代码中直接使用。 将对象添加到 ListBox 类中。 |
IList.Contains(Object) |
确定 IList 是否包含特定值。 |
IList.IndexOf(Object) |
确定 IList 中特定项的索引。 |
IList.Insert(Int32, Object) |
在 IList 中的指定索引处插入一个项。 |
IList.IsFixedSize |
有关此成员的说明,请参见 IsFixedSize。 |
IList.Item[Int32] |
获取或设置指定索引处的元素。 |
IList.Remove(Object) |
从 IList 中移除特定对象的第一个匹配项。 |
扩展方法
Cast<TResult>(IEnumerable) |
将 IEnumerable 的元素强制转换为指定的类型。 |
OfType<TResult>(IEnumerable) |
根据指定类型筛选 IEnumerable 的元素。 |
AsParallel(IEnumerable) |
启用查询的并行化。 |
AsQueryable(IEnumerable) |
将 IEnumerable 转换为 IQueryable。 |