BindingContext Class

Definition

Namespace:

System.Windows.Forms

Assembly:

System.Windows.Forms.dll

Source:

BindingContext.cs

Manages the collection of BindingManagerBase objects for any object that inherits from the Control class.

public ref class BindingContext : System::Collections::ICollection

public class BindingContext : System.Collections.ICollection

type BindingContext = class
    interface ICollection
    interface IEnumerable

Public Class BindingContext
Implements ICollection

Inheritance

Object

BindingContext

Implements

ICollection IEnumerable

Examples

The following code example creates four Binding objects to bind five controls - a DateTimePicker and four TextBox controls - to several data sources. The BindingContext is then used to get the BindingManagerBase for each data source.

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.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");
}

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

Remarks

Each Windows Form has at least one BindingContext object that manages the BindingManagerBase objects for the form. Because the BindingManagerBase class is abstract, the return type of the Item[] property is either a CurrencyManager or a PropertyManager. If the data source is an object that can return only a single property (instead of a list of objects), the Type is a PropertyManager. For example, if you specify a TextBox as the data source, a PropertyManager is returned. On the other hand, if the data source is an object that implements IList or IBindingList, a CurrencyManager is returned.

For each data source on a Windows Form, there is a single CurrencyManager or PropertyManager. Because there may be multiple data sources associated with a Windows Form, the BindingContext enables you to retrieve any particular CurrencyManager associated with a data source.

Note

When using the Item[] property, the BindingContext creates a new BindingManagerBase if one does not already exist. This can lead to some confusion, as the returned object may not manage the list (or any list) that you intend. To prevent returning an invalid BindingManagerBase, use the Contains method to determine if the intended BindingManagerBase already exists.

If you use a container control, such as a GroupBox, Panel, or TabControl, to contain data-bound controls, you can create a BindingContext for just that container control and its controls. Then, each part of your form can be managed by its own BindingManagerBase. See the BindingContext constructor for more information about creating multiple BindingManagerBase objects for the same data source.

If you add a TextBox control to a form and bind it to a column of a table in a dataset, the control communicates with the BindingContext of that form. The BindingContext, in turn, talks to the specific CurrencyManager for that data association. If you queried the Position property of the CurrencyManager, it would report the current record for the binding of that TextBox control. In the following code example, a TextBox control is bound to the FirstName column of a Customers table on the dataSet1 dataset through the BindingContext for the form it is on.

TextBox1.DataBindings.Add("Text", dataSet1, "Customers.FirstName")  

textBox1.DataBindings.Add("Text", dataSet1, "Customers.FirstName");  

textBox1->DataBindings->Add("Text", dataSet1, "Customers.FirstName");  

You can add a second TextBox control (TextBox2) to the form and bind it to the LastName column of the Customers table in the same dataset. The BindingContext is aware of the first binding (TextBox1 to Customers.FirstName), so it would use the same CurrencyManager, as both text boxes are bound to the same dataset (DataSet1).

TextBox2.DataBindings.Add("Text", dataSet1, "Customers.LastName")  

textBox2.DataBindings.Add("Text", dataSet1, "Customers.LastName");  

textBox2->DataBindings->Add("Text", dataSet1, "Customers.LastName");  

If you bind TextBox2 to a different dataset, the BindingContext creates and manages a second CurrencyManager.

It is important to be consistent about how you set the DataSource and DisplayMember properties; otherwise, the BindingContext creates multiple currency managers for the same dataset, which results in errors. The following code example shows a few ways to set the properties and their associated BindingContext objects. You can set the properties using either of the following methods, as long as you are consistent throughout your code.

ComboBox1.DataSource = DataSet1  
ComboBox1.DisplayMember = "Customers.FirstName"  
Me.BindingContext(dataSet1, "Customers").Position = 1  

comboBox1.DataSource = DataSet1;  
comboBox1.DisplayMember = "Customers.FirstName";  
this.BindingContext[dataSet1, "Customers"].Position = 1;  

comboBox1->DataSource = dataSet1;  
comboBox1->DisplayMember = "Customers.FirstName";  
this->BindingContext->get_Item(dataSet1, "Customers")->Position = 1;  

ComboBox1.DataSource = DataSet1.Customers  
ComboBox1.DisplayMember = "FirstName"  
Me.BindingContext(dataSet1.Customers).Position = 1  

comboBox1.DataSource = DataSet1.Customers;  
comboBox1.DisplayMember = "FirstName";  
this.BindingContext[dataSet1.Customers].Position = 1;  

comboBox1->DataSource = dataSet1->Customers;  
comboBox1->DisplayMember = "FirstName";  
this->BindingContext->get_Item(dataSet1->Customers)->Position = 1;  

Note

Most Windows Forms applications bind through a BindingSource. The BindingSource component encapsulates a CurrencyManager and exposes the CurrencyManager programming interface. When using a BindingSource for binding, you should use the members exposed by the BindingSource to manipulate "currency" (that is, Position) rather than go through the BindingContext.

Constructors

BindingContext()

Initializes a new instance of the BindingContext class.

Properties

IsReadOnly	Gets a value indicating whether the collection is read-only.
Item[Object, String]	Gets a BindingManagerBase that is associated with the specified data source and data member.
Item[Object]	Gets the BindingManagerBase that is associated with the specified data source.

Methods

Add(Object, BindingManagerBase)	Adds the BindingManagerBase associated with a specific data source to the collection.
AddCore(Object, BindingManagerBase)	Adds the BindingManagerBase associated with a specific data source to the collection.
Clear()	Clears the collection of any BindingManagerBase objects.
ClearCore()	Clears the collection.
Contains(Object, String)	Gets a value indicating whether the BindingContext contains the BindingManagerBase associated with the specified data source and data member.
Contains(Object)	Gets a value indicating whether the BindingContext contains the BindingManagerBase associated with the specified data source.
Equals(Object)	Determines whether the specified object is equal to the current object. (Inherited from Object)
GetHashCode()	Serves as the default hash function. (Inherited from Object)
GetType()	Gets the Type of the current instance. (Inherited from Object)
MemberwiseClone()	Creates a shallow copy of the current Object. (Inherited from Object)
OnCollectionChanged(CollectionChangeEventArgs)	Raises the CollectionChanged event.
Remove(Object)	Deletes the BindingManagerBase associated with the specified data source.
RemoveCore(Object)	Removes the BindingManagerBase associated with the specified data source.
ToString()	Returns a string that represents the current object. (Inherited from Object)
UpdateBinding(BindingContext, Binding)	Associates a Binding with a new BindingContext.

Events

CollectionChanged

Always raises a NotImplementedException when handled.

Explicit Interface Implementations

ICollection.CopyTo(Array, Int32)	Copies the elements of the collection into a specified array, starting at the collection index.
ICollection.Count	Gets the total number of CurrencyManager objects managed by the BindingContext.
ICollection.IsSynchronized	Gets a value indicating whether the collection is synchronized.
ICollection.SyncRoot	Gets an object to use for synchronization (thread safety).
IEnumerable.GetEnumerator()	Gets an enumerator for the collection.

Extension Methods

See also

• BindingManagerBase
• Binding
• BindingsCollection