Represents the simple binding between the property value of an object and the property value of a control.
Assembly: System.Windows.Forms (in System.Windows.Forms.dll)
Thetype exposes the following members.
|Binding(String, Object, String)||Initializes a new instance of the class that simple-binds the indicated control property to the specified data member of the data source.|
|Binding(String, Object, String, Boolean)||Initializes a new instance of the class that binds the indicated control property to the specified data member of the data source, and optionally enables formatting to be applied.|
|Binding(String, Object, String, Boolean, DataSourceUpdateMode)||Initializes a new instance of the class that binds the specified control property to the specified data member of the specified data source. Optionally enables formatting and propagates values to the data source based on the specified update setting.|
|Binding(String, Object, String, Boolean, DataSourceUpdateMode, Object)||Initializes a new instance of the class that binds the indicated control property to the specified data member of the specified data source. Optionally enables formatting, propagates values to the data source based on the specified update setting, and sets the property to the specified value when a DBNull is returned from the data source.|
|Binding(String, Object, String, Boolean, DataSourceUpdateMode, Object, String)||Initializes a new instance of the class that binds the specified control property to the specified data member of the specified data source. Optionally enables formatting with the specified format string; propagates values to the data source based on the specified update setting; and sets the property to the specified value when a DBNull is returned from the data source.|
|Binding(String, Object, String, Boolean, DataSourceUpdateMode, Object, String, IFormatProvider)||Initializes a new instance of the class with the specified control property to the specified data member of the specified data source. Optionally enables formatting with the specified format string; propagates values to the data source based on the specified update setting; enables formatting with the specified format string; sets the property to the specified value when a DBNull is returned from the data source; and sets the specified format provider.|
|BindableComponent||Gets the control the is associated with.|
|BindingManagerBase||Gets the BindingManagerBase for this .|
|BindingMemberInfo||Gets an object that contains information about this binding based on the dataMember parameter in the Binding constructor.|
|Control||Gets the control that the binding belongs to.|
|ControlUpdateMode||Gets or sets when changes to the data source are propagated to the bound control property.|
|DataSource||Gets the data source for this binding.|
|DataSourceNullValue||Gets or sets the value to be stored in the data source if the control value is Nothing or empty.|
|DataSourceUpdateMode||Gets or sets a value that indicates when changes to the bound control property are propagated to the data source.|
|FormatInfo||Gets or sets the IFormatProvider that provides custom formatting behavior.|
|FormatString||Gets or sets the format specifier characters that indicate how a value is to be displayed.|
|FormattingEnabled||Gets or sets a value indicating whether type conversion and formatting is applied to the control property data.|
|IsBinding||Gets a value indicating whether the binding is active.|
|NullValue||Gets or sets the Object to be set as the control property when the data source contains a DBNull value.|
|PropertyName||Gets or sets the name of the control's data-bound property.|
|Equals(Object)||Determines whether the specified object is equal to the current object. (Inherited from Object.)|
|Finalize||Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection. (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.)|
|OnBindingComplete||Raises the BindingComplete event.|
|OnFormat||Raises the Format event.|
|OnParse||Raises the Parse event.|
|ReadValue||Sets the control property to the value read from the data source.|
|ToString||Returns a string that represents the current object. (Inherited from Object.)|
|WriteValue||Reads the current value from the control property and writes it to the data source.|
|BindingComplete||Occurs when the FormattingEnabled property is set to true and a binding operation is complete, such as when data is pushed from the control to the data source or vice versa|
|Format||Occurs when the property of a control is bound to a data value.|
|Parse||Occurs when the value of a data-bound control changes.|
Use the class to create and maintain a simple binding between the property of a control and either the property of an object, or the property of the current object in a list of objects.
As an example of the first case, you can bind the Text property of a TextBox control to the FirstName property of a Customer object. As an example of the second case, you can bind the Text property of a TextBox control to the FirstName property of a DataTable that contains customers.
When constructing a instance with Binding constructor, you must specify three items:
The name of the control property to bind to.
The data source.
The navigation path that resolves to a list or property in the data source. The navigation path is also used to create the object's BindingMemberInfo property.
Second, you can specify an instance of any one of the classes in the following table as the data source.
DataSet ds = new DataSet("myDataSet");
Any class that implements IList to create an indexed collection of objects. The collection must be created and filled before creating the . The objects in the list must all be of the same type; otherwise, an exception will be thrown.
ArrayList ar1 = new ArrayList; Customer1 cust1 = new Customer("Louis"); ar1.Add(cust1);
A strongly typed IList of strongly typed objects
Customer  custList = new Customer;
Third, you must specify the navigation path, which can be an empty string (""), a single property name, or a period-delimited hierarchy of names. If you set the navigation path to an empty string, the ToString method will be called on the underlying data source object.
A period-delimited navigation path is required when the data source is set to an object that contains multiple DataTable objects (such as a DataSet or DataViewManager). You can also use a period-delimited navigation path when you bind to an object whose properties return references to other objects (such as a class with properties that return other class objects). For example, the following navigation paths all describe valid data fields:
Each member of the path can return either a property that resolves to a single value (such as an integer), or a list of values (such as an array of strings). Although each member in the path can be a list or property, the final member must resolve to a property. Each member builds on the previous member: "Size.Height" resolves to the Height property for the current Size; "Regions.regionsToCustomers.CustomerFirstName" resolves to the first name for the current customer, where the customer is one of the customers for the current region.
A DataRelation returns a list of values by linking one DataTable to a second DataTable in a DataSet. If the DataSet contains DataRelation objects, you can specify the data member as a TableName followed by a RelationName, and then a ColumnName. For example, if the DataTable named "Suppliers" contains a DataRelation named "suppliers2products", the data member could be "Suppliers.suppliers2products.ProductName".
The data source can consist of a set of related classes. For example, imagine a set of classes that catalogs solar systems. The class named System contains a property named Stars that returns a collection of Star objects. Each Star object has Name and Mass properties, as well as a Planets property that returns a collection of Planet objects. In this system, each planet also has Mass and Name properties. Each Planet object further has a Moons property that returns a collection of Moon objects, each of which also has Name and Mass properties. If you specify a System object as the data source, you can specify any of the following as the data member:
Controls that can be simple-bound feature a collection of objects in a ControlBindingsCollection, which you can access through the control's DataBindings property. You add a to the collection by calling the Add method, thereby binding a property of the control to a property of an object (or to a property of the current object in a list).
You can simple-bind to any object that derives from the System.Windows.Forms.Control class, for example, the following Windows controls:
The BindingManagerBase class is an abstract class that manages all the objects for a particular data source and data member. Classes that derive from BindingManagerBase are the CurrencyManager and the PropertyManager classes. How a is managed depends on whether the is a list binding or a property binding. For example, if it is a list binding, you can use the BindingManagerBase to specify a Position in the list; the Position, therefore, determines which item (out of all items in the list) is actually bound to a control. To return the appropriate BindingManagerBase, use the BindingContext.
To add a new row to a set of controls bound to the same DataSource, use the AddNew method of the BindingManagerBase class. Use the Item property of the BindingContext class to return the appropriate CurrencyManager. To escape the addition of the new row, use the CancelCurrentEdit method.
The following code example creates a Windows Form with several controls that demonstrate simple data binding. The example creates a DataSet with two tables named Customers and Orders, and a DataRelation named custToOrders. Four controls (a DateTimePicker and three TextBox controls) are data bound to columns in the tables. For each control, the example creates and adds a to the control through the DataBindings property. The example returns a BindingManagerBase for each table through the form's BindingContext. Four Button controls increment or decrement the Position property on the BindingManagerBase objects.
Imports System Imports System.ComponentModel Imports System.Data Imports System.Drawing Imports System.Globalization Imports System.Windows.Forms Public Class Form1 Inherits Form Private components As Container Private button1 As Button Private button2 As Button Private button3 As Button Private button4 As Button Private text1 As TextBox Private text2 As TextBox Private text3 As TextBox Private bmCustomers As BindingManagerBase Private bmOrders As BindingManagerBase Private ds As DataSet Private DateTimePicker1 As DateTimePicker Public Sub New ' Required for Windows Form Designer support. InitializeComponent ' Call SetUp to bind the controls. SetUp End Sub Protected Overloads Overrides Sub Dispose(ByVal disposing As Boolean) If disposing Then If (components IsNot Nothing) Then components.Dispose() End If End If MyBase.Dispose(disposing) End Sub Private Sub InitializeComponent ' Create the form and its controls. With Me .components = New Container .button1 = New Button .button2 = New Button .button3 = New Button .button4 = New Button .text1 = New TextBox .text2 = New TextBox .text3 = New TextBox .DateTimePicker1 = New DateTimePicker .Text = "Binding Sample" .ClientSize = New Size(450, 200) With .button1 .Location = New Point(24, 16) .Size = New Size(64, 24) .Text = "<" AddHandler button1.click, AddressOf button1_Click End With With .button2 .Location = New Point(90, 16) .Size = New Size(64, 24) .Text = ">" AddHandler button2.click, AddressOf button2_Click End With With .button3 .Location = New Point(90, 100) .Size = New Size(64, 24) .Text = ">" AddHandler button3.click, AddressOf button3_Click End With With .button4 .Location = New Point(150, 100) .Size = New Size(64, 24) .Text = ">" AddHandler button4.click, AddressOf button4_Click End With With .text1 .Location = New Point(24, 50) .Size = New Size(150, 24) End With With .text2 .Location = New Point(190, 50) .Size = New Size(150, 24) End With With .text3 .Location = New Point(290, 150) .Size = New Size(150, 24) End With With .DateTimePicker1 .Location = New Point(90, 150) .Size = New Size(200, 800) End With With .Controls .Add(button1) .Add(button2) .Add(button3) .Add(button4) .Add(text1) .Add(text2) .Add(text3) .Add(DateTimePicker1) End With End With End Sub Public Shared Sub Main Application.Run(new Form1) End Sub Private Sub SetUp ' Create a DataSet with two tables and one relation. MakeDataSet BindControls End Sub Private 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 ' TableName.ColumnName" string. 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, AddressOf CurrencyStringToDecimal AddHandler b.Format, 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") End Sub Private Sub DecimalToCurrencyString(sender As Object, cevent As 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". ' The application can only convert to string type. If cevent.DesiredType IsNot GetType(String) Then Exit Sub End If cevent.Value = CType(cevent.Value, decimal).ToString("c") End Sub Private Sub CurrencyStringToDecimal(sender As Object, cevent As 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 IsNot GetType(decimal) Then Exit Sub End If cevent.Value = Decimal.Parse(cevent.Value.ToString, _ NumberStyles.Currency, nothing) ' 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) End Sub Private Sub button1_Click(sender As Object, e As System.EventArgs) ' Go to the previous item in the Customer list. bmCustomers.Position -= 1 End Sub Private Sub button2_Click(sender As Object, e As System.EventArgs) ' Go to the next item in the Customer list. bmCustomers.Position += 1 End Sub Private Sub button3_Click(sender As Object, e As System.EventArgs) ' Go to the previous item in the Order list. bmOrders.Position -= 1 End Sub Private Sub button4_Click(sender As Object, e As System.EventArgs) ' Go to the next item in the Orders list. bmOrders.Position += 1 End Sub ' Creates a DataSet with two tables and populates it. Private Sub MakeDataSet ' Create a DataSet. ds = New DataSet("myDataSet") ' Creates two DataTables. Dim tCust As DataTable = New DataTable("Customers") Dim tOrders As DataTable = New DataTable("Orders") ' Create two columns, and add them to the first table. Dim cCustID As DataColumn = New DataColumn("CustID", _ System.Type.GetType("System.Int32")) Dim cCustName As DataColumn = New DataColumn("CustName") tCust.Columns.Add(cCustID) tCust.Columns.Add(cCustName) ' Create three columns, and add them to the second table. Dim cID As DataColumn = _ New DataColumn("CustID", System.Type.GetType("System.Int32")) Dim cOrderDate As DataColumn = _ New DataColumn("orderDate", System.Type.GetType("System.DateTime")) Dim cOrderAmount As DataColumn = _ New DataColumn("OrderAmount", System.Type.GetType("System.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. Dim dr As DataRelation = New _ DataRelation("custToOrders", cCustID, cID) ds.Relations.Add(dr) ' Populate the tables. For each customer and orders, ' create two DataRow variables. Dim newRow1 As DataRow Dim newRow2 As DataRow ' Create three customers in the Customers Table. Dim i As Integer For i = 1 to 3 newRow1 = tCust.NewRow newRow1("custID") = i ' Adds the row to the Customers table. tCust.Rows.Add(newRow1) Next ' 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. Dim j As Integer For i = 1 to 3 For j = 1 to 5 newRow2 = tOrders.NewRow newRow2("CustID") = i newRow2("orderDate") = New DateTime(2001, i, j * 2) newRow2("OrderAmount") = i * 10 + j * .1 ' Add the row to the Orders table. tOrders.Rows.Add(newRow2) Next Next End Sub End Class