How to: Bind a Windows Forms Control to a Factory Object

When you are building controls that interact with data, you will sometimes find it necessary to bind a control to an object or method that generates other objects. Such an object or method is called a factory. Your data source might be, for example, the return value from a method call, instead of an object in memory or a type. You can bind a control to this kind of data source as long as the source returns a collection.

You can easily bind a control to a factory object by using the BindingSource control.

Example

The following example demonstrates how to bind a DataGridView control to a factory method by using a BindingSource control. The factory method is named GetOrdersByCustomerId, and it returns all the orders for a given customer in the Northwind database.

#using <System.dll>
#using <System.Data.dll>
#using <System.Drawing.dll>
#using <System.EnterpriseServices.dll>
#using <System.Transactions.dll>
#using <System.Windows.Forms.dll>
#using <System.Xml.dll>
using namespace System;
using namespace System::Collections;
using namespace System::Collections::Generic;
using namespace System::ComponentModel;
using namespace System::Data;
using namespace System::Data::Common;
using namespace System::Data::SqlClient;
using namespace System::Diagnostics;
using namespace System::Drawing;
using namespace System::Windows::Forms;

// This form demonstrates using a BindingSource to bind to a factory
// object.
public ref class Form1: public System::Windows::Forms::Form
{
private:

 // This is the TextBox for entering CustomerID values.
 static TextBox^ customerIdTextBox = gcnew TextBox;

 // This is the DataGridView that displays orders for the
 // specified customer.
 static DataGridView^ customersDataGridView = gcnew DataGridView;

 // This is the BindingSource for binding the database query
 // result set to the DataGridView.
 static BindingSource^ ordersBindingSource = gcnew BindingSource;

public:
 Form1()
 {
 // Set up the CustomerID TextBox.
 this->customerIdTextBox->Dock = DockStyle::Bottom;
 this->customerIdTextBox->Text =
 L"Enter a valid Northwind CustomerID, for example: ALFKI,"

 L" then TAB or click outside the TextBox";
 this->customerIdTextBox->Leave += gcnew EventHandler(
 this, &Form1::customerIdTextBox_Leave );
 this->Controls->Add( this->customerIdTextBox );
 
 // Set up the DataGridView.
 customersDataGridView->Dock = DockStyle::Top;
 this->Controls->Add( customersDataGridView );
 
 // Set up the form.
 this->Size = System::Drawing::Size( 800, 800 );
 this->Load += gcnew EventHandler( this, &Form1::Form1_Load );
 }

private:
 // This event handler binds the BindingSource to the DataGridView
 // control's DataSource property.
 void Form1_Load(
 System::Object^ /*sender*/,
 System::EventArgs^ /*e*/ )
 {
 // Attach the BindingSource to the DataGridView.
 this->customersDataGridView->DataSource =
 this->ordersBindingSource;
 }

public:
 // This is a static factory method. It queries the Northwind
 // database for the orders belonging to the specified
 // customer and returns an IList.
 static System::Collections::IList^ GetOrdersByCustomerId( String^ id )
 {
 // Open a connection to the database.
 String^ connectString = L"Integrated Security=SSPI;"
 L"Persist Security Info=False;Initial Catalog=Northwind;"
 L"Data Source= localhost";
 SqlConnection^ connection = gcnew SqlConnection;
 connection->ConnectionString = connectString;
 connection->Open();
 
 // Execute the query.
 String^ queryString = String::Format(
 L"Select * From Orders where CustomerID = '{0}'", id );
 SqlCommand^ command = gcnew SqlCommand( queryString,connection );
 SqlDataReader^ reader = command->ExecuteReader(
 CommandBehavior::CloseConnection );
 
 // Build an IList from the result set.
 List< DbDataRecord^ >^ list = gcnew List< DbDataRecord^ >;
 System::Collections::IEnumerator^ e = reader->GetEnumerator();
 while ( e->MoveNext() )
 {
 list->Add( dynamic_cast<DbDataRecord^>(e->Current) );
 }

 return list;
 }

 // This event handler is called when the user tabs or clicks
 // out of the customerIdTextBox. The database is then queried
 // with the CustomerID in the customerIdTextBox.Text property.
private:
 void customerIdTextBox_Leave( Object^ /*sender*/, EventArgs^ /*e*/ )
 {
 // Attach the data source to the BindingSource control.
 this->ordersBindingSource->DataSource = GetOrdersByCustomerId(
 this->customerIdTextBox->Text );
 }

public:
 [STAThread]
 static void main()
 {
 Application::EnableVisualStyles();
 Application::Run( gcnew Form1 );
 }
};

using System;
using System.Collections;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Data.Common;
using System.Diagnostics;
using System.Drawing;
using System.Data.SqlClient;
using System.Windows.Forms;

// This form demonstrates using a BindingSource to bind to a factory
// object.
public class Form1 : System.Windows.Forms.Form
{
 // This is the TextBox for entering CustomerID values.
 private TextBox customerIdTextBox = new TextBox();

 // This is the DataGridView that displays orders for the
 // specified customer.
 private DataGridView customersDataGridView = new DataGridView();

 // This is the BindingSource for binding the database query
 // result set to the DataGridView.
 private BindingSource ordersBindingSource = new BindingSource();

 public Form1()
 {
 // Set up the CustomerID TextBox.
 this.customerIdTextBox.Location = new Point(100, 200);
 this.customerIdTextBox.Size = new Size(500, 30);
 this.customerIdTextBox.Text =
 "Enter a valid Northwind CustomerID, for example: ALFKI," +
 " then RETURN or click outside the TextBox";
 this.customerIdTextBox.Leave +=
 new EventHandler(customerIdTextBox_Leave);
 this.customerIdTextBox.KeyDown +=
 new KeyEventHandler(customerIdTextBox_KeyDown);
 this.Controls.Add(this.customerIdTextBox);

 // Set up the DataGridView.
 customersDataGridView.Dock = DockStyle.Top;
 this.Controls.Add(customersDataGridView);

 // Set up the form.
 this.Size = new Size(800, 500);
 this.Load += new EventHandler(Form1_Load);
 }

 // This event handler binds the BindingSource to the DataGridView
 // control's DataSource property.
 private void Form1_Load(
 System.Object sender,
 System.EventArgs e)
 {
 // Attach the BindingSource to the DataGridView.
 this.customersDataGridView.DataSource =
 this.ordersBindingSource;
 }

 // This is a static factory method. It queries the Northwind
 // database for the orders belonging to the specified
 // customer and returns an IEnumerable.
 public static IEnumerable GetOrdersByCustomerId(string id)
 {
 // Open a connection to the database.
 string connectString = "Integrated Security=SSPI;" +
 "Persist Security Info=False;Initial Catalog=Northwind;" +
 "Data Source= localhost";
 SqlConnection connection = new SqlConnection();

 connection.ConnectionString = connectString;
 connection.Open();

 // Execute the query.
 string queryString =
 String.Format("Select * From Orders where CustomerID = '{0}'",
 id);
 SqlCommand command = new SqlCommand(queryString, connection);
 SqlDataReader reader =
 command.ExecuteReader(CommandBehavior.CloseConnection);
 return reader;
 }

 // These event handlers are called when the user tabs or clicks
 // out of the customerIdTextBox or hits the return key.
 // The database is then queried with the CustomerID
 // in the customerIdTextBox.Text property.
 void customerIdTextBox_Leave(object sender, EventArgs e)
 {
 // Attach the data source to the BindingSource control.
 this.ordersBindingSource.DataSource =
 GetOrdersByCustomerId(this.customerIdTextBox.Text);
 }

 void customerIdTextBox_KeyDown(object sender, KeyEventArgs e)
 {
 if (e.KeyCode == Keys.Return)
 {
 // Attach the data source to the BindingSource control.
 this.ordersBindingSource.DataSource =
 GetOrdersByCustomerId(this.customerIdTextBox.Text);
 }
 }

 [STAThread]
 static void Main()
 {
 Application.EnableVisualStyles();
 Application.Run(new Form1());
 }
}

Imports System.Collections
Imports System.Collections.Generic
Imports System.ComponentModel
Imports System.Data
Imports System.Data.Common
Imports System.Diagnostics
Imports System.Drawing
Imports System.Data.SqlClient
Imports System.Windows.Forms

' This form demonstrates using a BindingSource to bind to a factory
' object. 

Public Class Form1
 Inherits System.Windows.Forms.Form
 ' This is the TextBox for entering CustomerID values.
 Private WithEvents customerIdTextBox As New TextBox()
 
 ' This is the DataGridView that displays orders for the 
 ' specified customer.
 Private customersDataGridView As New DataGridView()
 
 ' This is the BindingSource for binding the database query
 ' result set to the DataGridView.
 Private ordersBindingSource As New BindingSource()
 
 Public Sub New() 

 ' Set up the CustomerID TextBox.
 Me.customerIdTextBox.Location = New Point(100, 200)
 Me.customerIdTextBox.Size = New Size(500, 30)
 Me.customerIdTextBox.Text = _
 "Enter a valid Northwind CustomerID, for example: ALFKI," & _
 " then RETURN or click outside the TextBox"
 Me.Controls.Add(Me.customerIdTextBox)
 
 ' Set up the DataGridView.
 customersDataGridView.Dock = DockStyle.Top
 Me.Controls.Add(customersDataGridView)
 
 ' Set up the form.
 Me.Size = New Size(800, 500)
 End Sub
 
 ' This event handler binds the BindingSource to the DataGridView
 ' control's DataSource property.
 Private Sub Form1_Load(ByVal sender As System.Object, _
 ByVal e As System.EventArgs) Handles Me.Load

 ' Attach the BindingSource to the DataGridView.
 Me.customersDataGridView.DataSource = Me.ordersBindingSource

 End Sub
 
 ' This is a static factory method. It queries the Northwind 
 ' database for the orders belonging to the specified
 ' customer and returns an IEnumerable.
 Public Shared Function GetOrdersByCustomerId(ByVal id As String) _
 As IEnumerable

 ' Open a connection to the database.
 Dim connectString As String = "Integrated Security=SSPI;" & _
 "Persist Security Info=False;Initial Catalog=Northwind;" & _
 "Data Source= localhost"
 Dim connection As New SqlConnection()

 connection.ConnectionString = connectString
 connection.Open()

 ' Execute the query.
 Dim queryString As String = _
 String.Format("Select * From Orders where CustomerID = '{0}'", id)
 Dim command As New SqlCommand(queryString, connection)
 Dim reader As SqlDataReader = _
 command.ExecuteReader(CommandBehavior.CloseConnection)
 Return reader

 End Function
 
 ' These event handlers are called when the user tabs or clicks
 ' out of the customerIdTextBox or hits the return key.
 ' The database is then queried with the CustomerID
 ' in the customerIdTextBox.Text property.
 Private Sub customerIdTextBox_Leave(ByVal sender As Object, _
 ByVal e As EventArgs) Handles customerIdTextBox.Leave

 ' Attach the data source to the BindingSource control.
 Me.ordersBindingSource.DataSource = _
 GetOrdersByCustomerId(Me.customerIdTextBox.Text)

 End Sub
 
 
 Private Sub customerIdTextBox_KeyDown(ByVal sender As Object, _
 ByVal e As KeyEventArgs) Handles customerIdTextBox.KeyDown

 If e.KeyCode = Keys.Return Then

 ' Attach the data source to the BindingSource control.
 Me.ordersBindingSource.DataSource = _
 GetOrdersByCustomerId(Me.customerIdTextBox.Text)
 End If

 End Sub

 <STAThread()> _
 Shared Sub Main()
 Application.EnableVisualStyles()
 Application.Run(New Form1())

 End Sub
End Class

Compiling the Code

This example requires:

• References to the System, System.Data, System.Drawing and System.Windows.Forms assemblies.

See also

• BindingNavigator
• DataGridView
• BindingSource
• BindingSource Component
• How to: Bind a Windows Forms Control to a Type