Control.BindingContext-Eigenschaft
Ruft den BindingContext für das Steuerelement ab oder legt diesen fest.
Namespace: System.Windows.Forms
Assembly: System.Windows.Forms (in system.windows.forms.dll)
Syntax
'Declaration
Public Overridable Property BindingContext As BindingContext
'Usage
Dim instance As Control
Dim value As BindingContext
value = instance.BindingContext
instance.BindingContext = value
public virtual BindingContext BindingContext { get; set; }
public:
virtual property BindingContext^ BindingContext {
BindingContext^ get ();
void set (BindingContext^ value);
}
/** @property */
public BindingContext get_BindingContext ()
/** @property */
public void set_BindingContext (BindingContext value)
public function get BindingContext () : BindingContext
public function set BindingContext (value : BindingContext)
Eigenschaftenwert
Ein BindingContext für das Steuerelement.
Hinweise
Der BindingContext eines Control wird verwendet, um ein einzelnes BindingManagerBase-Objekt für alle im Control enthaltenen datengebundenen Steuerelemente zurückzugeben. BindingManagerBase synchronisiert alle an dieselbe Datenquelle gebundenen Steuerelemente. Durch Festlegen der Position-Eigenschaft der BindingManagerBase wird z. B. das Element in der zugrunde liegenden Liste angegeben, auf das alle datengebundenen Steuerelemente zeigen.
Weitere Informationen zum Erstellen eines neuen BindingContext und zum Zuweisen zur BindingContext-Eigenschaft finden Sie unter BindingContext.
Hinweise für Erben Verwenden Sie beim Überschreiben der BindingContext-Eigenschaft in einer abgeleiteten Klasse die BindingContext-Eigenschaft der Basisklasse, um die Basisimplementierung zu erweitern. Andernfalls müssen Sie die gesamte Implementierung bereitstellen. Sie müssen nicht sowohl den get-Accessor als auch den set-Accessor der BindingContext-Eigenschaft überschreiben. Sie können ggf. auch nur einen Accessor überschreiben.
Beispiel
Im folgenden Codebeispiel werden vier Binding-Objekte erstellt, um fünf Steuerelemente, d. h. ein DateTimePicker-Steuerelement und vier TextBox-Steuerelemente, an verschiedene Datenquellen zu binden. Mithilfe von BindingContext wird dann die BindingManagerBase für jede Datenquelle abgerufen.
Protected Sub BindControls()
' Create two Binding objects for the first two TextBox
' controls. The data-bound property for both controls
' is the Text property. The data source is a DataSet
' (ds). The data member is the string
' "TableName.ColumnName".
text1.DataBindings.Add(New Binding _
("Text", ds, "customers.custName"))
text2.DataBindings.Add(New Binding _
("Text", ds, "customers.custID"))
' Bind the DateTimePicker control by adding a new Binding.
' The data member of the DateTimePicker is a
' TableName.RelationName.ColumnName string.
DateTimePicker1.DataBindings.Add(New Binding _
("Value", ds, "customers.CustToOrders.OrderDate"))
' Add event delegates for the Parse and Format events to a
' new Binding object, and add the object to the third
' TextBox control's BindingsCollection. The delegates
' must be added before adding the Binding to the
' collection; otherwise, no formatting occurs until
' the Current object of the BindingManagerBase for
' the data source changes.
Dim b As Binding = New Binding _
("Text", ds, "customers.custToOrders.OrderAmount")
AddHandler b.Parse, New ConvertEventHandler(AddressOf CurrencyStringToDecimal)
AddHandler b.Format, New ConvertEventHandler(AddressOf DecimalToCurrencyString)
text3.DataBindings.Add(b)
' Get the BindingManagerBase for the Customers table.
bmCustomers = Me.BindingContext(ds, "Customers")
' Get the BindingManagerBase for the Orders table using the
' RelationName.
bmOrders = Me.BindingContext(ds, "customers.CustToOrders")
' Bind the fourth TextBox control's Text property to the
' third control's Text property.
text4.DataBindings.Add("Text", text3, "Text")
End Sub
protected void BindControls()
{
/* Create two Binding objects for the first two TextBox
controls. The data-bound property for both controls
is the Text property. The data source is a DataSet
(ds). The data member is a navigation path in the form:
"TableName.ColumnName". */
text1.DataBindings.Add(new Binding
("Text", ds, "customers.custName"));
text2.DataBindings.Add(new Binding
("Text", ds, "customers.custID"));
/* Bind the DateTimePicker control by adding a new Binding.
The data member of the DateTimePicker is a navigation path:
TableName.RelationName.ColumnName string. */
DateTimePicker1.DataBindings.Add(new
Binding("Value", ds, "customers.CustToOrders.OrderDate"));
/* Add event delegates for the Parse and Format events to a
new Binding object, and add the object to the third
TextBox control's BindingsCollection. The delegates
must be added before adding the Binding to the
collection; otherwise, no formatting occurs until
the Current object of the BindingManagerBase for
the data source changes. */
Binding b = new Binding
("Text", ds, "customers.custToOrders.OrderAmount");
b.Parse+=new ConvertEventHandler(CurrencyStringToDecimal);
b.Format+=new ConvertEventHandler(DecimalToCurrencyString);
text3.DataBindings.Add(b);
// Get the BindingManagerBase for the Customers table.
bmCustomers = this.BindingContext [ds, "Customers"];
/* Get the BindingManagerBase for the Orders table using the
RelationName. */
bmOrders = this.BindingContext[ds, "customers.CustToOrders"];
/* Bind the fourth TextBox control's Text property to the
third control's Text property. */
text4.DataBindings.Add("Text", text3, "Text");
}
void BindControls()
{
/* Create two Binding objects for the first two TextBox
controls. The data-bound property for both controls
is the Text property. The data source is a DataSet
(ds). The data member is a navigation path in the form:
"TableName.ColumnName". */
text1->DataBindings->Add( gcnew Binding( "Text",ds,"customers.custName" ) );
text2->DataBindings->Add( gcnew Binding( "Text",ds,"customers.custID" ) );
/* Bind the DateTimePicker control by adding a new Binding.
The data member of the DateTimePicker is a navigation path:
TableName.RelationName.ColumnName string. */
DateTimePicker1->DataBindings->Add( gcnew Binding( "Value",ds,"customers.CustToOrders.OrderDate" ) );
/* Add event delegates for the Parse and Format events to a
new Binding object, and add the object to the third
TextBox control's BindingsCollection. The delegates
must be added before adding the Binding to the
collection; otherwise, no formatting occurs until
the Current object of the BindingManagerBase for
the data source changes. */
Binding^ b = gcnew Binding( "Text",ds,"customers.custToOrders.OrderAmount" );
b->Parse += gcnew ConvertEventHandler( this, &Form1::CurrencyStringToDecimal );
b->Format += gcnew ConvertEventHandler( this, &Form1::DecimalToCurrencyString );
text3->DataBindings->Add( b );
// Get the BindingManagerBase for the Customers table.
bmCustomers = this->BindingContext[ ds,"Customers" ];
/* Get the BindingManagerBase for the Orders table using the
RelationName. */
bmOrders = this->BindingContext[ds, "customers.CustToOrders"];
/* Bind the fourth TextBox control's Text property to the
third control's Text property. */
text4->DataBindings->Add( "Text", text3, "Text" );
}
protected void BindControls()
{
/* Create two Binding objects for the first two TextBox
controls. The data-bound property for both controls
is the Text property. The data source is a DataSet
(ds). The data member is a navigation path in the form:
"TableName.ColumnName".
*/
text1.get_DataBindings().Add(new Binding("Text", ds,
"customers.custName"));
text2.get_DataBindings().Add(new Binding("Text", ds,
"customers.custID"));
/* Bind the DateTimePicker control by adding a new Binding.
The data member of the DateTimePicker is a navigation path:
TableName.RelationName.ColumnName string.
*/
dateTimePicker1.get_DataBindings().Add(new Binding("Value", ds,
"customers.CustToOrders.OrderDate"));
/* Add event delegates for the Parse and Format events to a
new Binding object, and add the object to the third
TextBox control's BindingsCollection. The delegates
must be added before adding the Binding to the
collection; otherwise, no formatting occurs until
the Current object of the BindingManagerBase for
the data source changes.
*/
Binding b = new Binding("Text", ds,
"customers.custToOrders.OrderAmount");
b.add_Parse(new ConvertEventHandler(CurrencyStringToDecimal));
b.add_Format(new ConvertEventHandler(DecimalToCurrencyString));
text3.get_DataBindings().Add(b);
// Get the BindingManagerBase for the Customers table.
bmCustomers = this.get_BindingContext().get_Item(ds, "Customers");
/* Get the BindingManagerBase for the Orders table using the
RelationName.
*/
bmOrders = this.get_BindingContext().get_Item(ds,
"customers.CustToOrders");
/* Bind the fourth TextBox control's Text property to the
third control's Text property.
*/
text4.get_DataBindings().Add("Text", text3, "Text");
} //BindControls
protected function BindControls()
{
/* Create two Binding objects for the first two TextBox
controls. The data-bound property for both controls
is the Text property. The data source is a DataSet
(ds). The data member is the string
"TableName.ColumnName". */
text1.DataBindings.Add(new Binding
("Text", ds, "customers.custName"));
text2.DataBindings.Add(new Binding
("Text", ds, "customers.custID"));
/* Bind the DateTimePicker control by adding a new Binding.
The data member of the DateTimePicker is a
TableName.RelationName.ColumnName string. */
DateTimePicker1.DataBindings.Add(new
Binding("Value", ds, "customers.CustToOrders.OrderDate"));
/* Add event delegates for the Parse and Format events to a
new Binding object, and add the object to the third
TextBox control's BindingsCollection. The delegates
must be added before adding the Binding to the
collection; otherwise, no formatting occurs until
the Current object of the BindingManagerBase for
the data source changes. */
var b : Binding = new Binding
("Text", ds, "customers.custToOrders.OrderAmount");
b.add_Parse(CurrencyStringToDecimal);
b.add_Format(DecimalToCurrencyString);
text3.DataBindings.Add(b);
// Get the BindingManagerBase for the Customers table.
bmCustomers = this.BindingContext [ds, "Customers"];
/* Get the BindingManagerBase for the Orders table using the
RelationName. */
bmOrders = this.BindingContext[ds, "customers.CustToOrders"];
}
private function DecimalToCurrencyString(sender, cevent : ConvertEventArgs)
{
/* This method is the Format event handler. Whenever the
control displays a new value, the value is converted from
its native Decimal type to a string. The ToString method
then formats the value as a Currency, by using the
formatting character "c". */
// We can only convert to string type.
if(cevent.DesiredType != String.GetType()) return;
cevent.Value = (Decimal(cevent.Value)).ToString("c");
}
private function CurrencyStringToDecimal(sender, cevent : ConvertEventArgs)
{
/* This method is the Parse event-handler. The Parse event
occurs whenever the displayed value changes. The static
ToDecimal method of the Convert class converts the
value back to its native Decimal type. */
// Can only convert to Decimal type.
if(cevent.DesiredType != Decimal.GetType()) return;
cevent.Value = Decimal.Parse(cevent.Value.ToString(),
NumberStyles.Currency, null);
/* To see that no precision is lost, print the unformatted
value. For example, changing a value to "10.0001"
causes the control to display "10.00", but the
unformatted value remains "10.0001". */
Console.WriteLine(cevent.Value);
}
protected function button1_Click(sender, e : System.EventArgs)
{
// Go to the previous item in the Customer list.
bmCustomers.Position -= 1;
}
protected function button2_Click(sender, e : System.EventArgs)
{
// Go to the next item in the Customer list.
bmCustomers.Position += 1;
}
protected function button3_Click(sender, e : System.EventArgs)
{
// Go to the previous item in the Orders list.
bmOrders.Position-=1;
}
protected function button4_Click(sender, e : System.EventArgs)
{
// Go to the next item in the Orders list.
bmOrders.Position+=1;
}
// Create a DataSet with two tables and populate it.
private function MakeDataSet()
{
// Create a DataSet.
ds = new DataSet("myDataSet");
// Create two DataTables.
var tCust : DataTable = new DataTable("Customers");
var tOrders : DataTable= new DataTable("Orders");
// Create two columns, and add them to the first table.
var cCustID : DataColumn = new DataColumn("CustID", Int32);
var cCustName : DataColumn = new DataColumn("CustName");
tCust.Columns.Add(cCustID);
tCust.Columns.Add(cCustName);
// Create three columns, and add them to the second table.
var cID : DataColumn =
new DataColumn("CustID", Int32);
var cOrderDate : DataColumn =
new DataColumn("orderDate", DateTime);
var cOrderAmount : DataColumn =
new DataColumn("OrderAmount", Decimal);
tOrders.Columns.Add(cOrderAmount);
tOrders.Columns.Add(cID);
tOrders.Columns.Add(cOrderDate);
// Add the tables to the DataSet.
ds.Tables.Add(tCust);
ds.Tables.Add(tOrders);
// Create a DataRelation, and add it to the DataSet.
var dr : DataRelation = new DataRelation
("custToOrders", cCustID , cID);
ds.Relations.Add(dr);
/* Populate the tables. For each customer and order,
create need two DataRow variables. */
var newRow1 : DataRow;
var newRow2 : DataRow;
// Create three customers in the Customers Table.
for(var i : int = 1; i < 4; i++)
{
newRow1 = tCust.NewRow();
newRow1["custID"] = i;
// Add the row to the Customers table.
tCust.Rows.Add(newRow1);
}
// Give each customer a distinct name.
tCust.Rows[0]["custName"] = "Alpha";
tCust.Rows[1]["custName"] = "Beta";
tCust.Rows[2]["custName"] = "Omega";
// For each customer, create five rows in the Orders table.
for(var j : int = 1; j < 4; j++)
{
for(var k : int = 1; k < 6; k++)
{
newRow2 = tOrders.NewRow();
newRow2["CustID"]= j;
newRow2["orderDate"]= new DateTime(2001, j, k * 2);
newRow2["OrderAmount"] = j * 10 + k * .1;
// Add the row to the Orders table.
tOrders.Rows.Add(newRow2);
}
}
}
}
Plattformen
Windows 98, Windows 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile für Pocket PC, Windows Mobile für Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition
.NET Framework unterstützt nicht alle Versionen sämtlicher Plattformen. Eine Liste der unterstützten Versionen finden Sie unter Systemanforderungen.
Versionsinformationen
.NET Framework
Unterstützt in: 2.0, 1.1, 1.0
.NET Compact Framework
Unterstützt in: 2.0, 1.0
Siehe auch
Referenz
Control-Klasse
Control-Member
System.Windows.Forms-Namespace
BindingContextChanged
Binding-Klasse
BindingManagerBase-Klasse