Procedura: riflettere gli aggiornamenti dell'origine dati in un controllo Windows Form con BindingSource
Quando si utilizzano controlli associati a dati, in alcuni casi è necessario rispondere alle modifiche che si sono verificate nell'origine dati, nel caso in cui quest'ultima non preveda la generazione di eventi di lista modificata. Quando si utilizza il componente BindingSource per associare l'origine dati a un controllo Windows Form, è possibile inviare al controllo la notifica di modifica dell'origine dati chiamando il metodo ResetBindings.
Esempio
Nell'esempio di codice riportato di seguito viene illustrato l'utilizzo del metodo ResetBindings per notificare a un controllo associato che l'origine dati è stata aggiornata.
Imports System
Imports System.ComponentModel
Imports System.Drawing
Imports System.Text
Imports System.Windows.Forms
Imports System.Collections
Class Form1
Inherits Form
' Declare the objects on the form.
Private label1 As Label
Private label2 As Label
Private textBox1 As TextBox
Private textBox2 As TextBox
Private WithEvents button1 As Button
Private bindingSource1 As BindingSource
Private states As ArrayList
Public Sub New()
' Basic form setup.
Me.button1 = New System.Windows.Forms.Button()
Me.textBox1 = New System.Windows.Forms.TextBox()
Me.label1 = New System.Windows.Forms.Label()
Me.label2 = New System.Windows.Forms.Label()
Me.textBox2 = New System.Windows.Forms.TextBox()
Me.button1.Location = New System.Drawing.Point(12, 18)
Me.button1.Size = New System.Drawing.Size(119, 38)
Me.button1.Text = "RemoveAt(0)"
Me.textBox1.Location = New System.Drawing.Point(55, 75)
Me.textBox1.ReadOnly = True
Me.textBox1.Size = New System.Drawing.Size(119, 20)
Me.label1.Location = New System.Drawing.Point(12, 110)
Me.label1.Size = New System.Drawing.Size(43, 14)
Me.label1.Text = "Capital:"
Me.label2.Location = New System.Drawing.Point(12, 78)
Me.label2.Size = New System.Drawing.Size(34, 14)
Me.label2.Text = "State:"
Me.textBox2.Location = New System.Drawing.Point(55, 110)
Me.textBox2.Size = New System.Drawing.Size(119, 20)
Me.textBox2.ReadOnly = True
Me.ClientSize = New System.Drawing.Size(292, 273)
Me.Controls.Add(Me.textBox2)
Me.Controls.Add(Me.label2)
Me.Controls.Add(Me.label1)
Me.Controls.Add(Me.textBox1)
Me.Controls.Add(Me.button1)
Me.Text = "Form1"
' Create an ArrayList containing some of the State objects.
states = New ArrayList()
states.Add(New State("California", "Sacramento"))
states.Add(New State("Oregon", "Salem"))
states.Add(New State("Washington", "Olympia"))
states.Add(New State("Idaho", "Boise"))
states.Add(New State("Utah", "Salt Lake City"))
states.Add(New State("Hawaii", "Honolulu"))
states.Add(New State("Colorado", "Denver"))
states.Add(New State("Montana", "Helena"))
bindingSource1 = New BindingSource()
' Bind BindingSource1 to the list of states.
bindingSource1.DataSource = states
' Bind the two text boxes to properties of State.
textBox1.DataBindings.Add("Text", bindingSource1, "Name")
textBox2.DataBindings.Add("Text", bindingSource1, "Capital")
End Sub
Private Sub button1_Click(ByVal sender As Object, ByVal e As EventArgs) _
Handles button1.Click
' If items remain in the list, remove the first item.
If states.Count > 0 Then
states.RemoveAt(0)
' Call ResetBindings to update the textboxes.
bindingSource1.ResetBindings(False)
End If
End Sub 'button1_Click
<STAThread()> _
Shared Sub Main()
Application.EnableVisualStyles()
Application.Run(New Form1())
End Sub
' The State class to add to the ArrayList.
Private Class State
Private stateName As String
Public ReadOnly Property Name() As String
Get
Return stateName
End Get
End Property
Private stateCapital As String
Public ReadOnly Property Capital() As String
Get
Return stateCapital
End Get
End Property
Public Sub New(ByVal name As String, ByVal capital As String)
stateName = name
stateCapital = capital
End Sub
End Class
End Class
using System;
using System.ComponentModel;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using System.Collections;
namespace System_Windows_Forms_UpdateBinding
{
class Form1 : Form
{
// Declare the objects on the form.
private Label label1;
private Label label2;
private TextBox textBox1;
private TextBox textBox2;
private Button button1;
private BindingSource bindingSource1;
ArrayList states;
public Form1()
{
// Basic form setup.
this.button1 = new System.Windows.Forms.Button();
this.textBox1 = new System.Windows.Forms.TextBox();
this.label1 = new System.Windows.Forms.Label();
this.label2 = new System.Windows.Forms.Label();
this.textBox2 = new System.Windows.Forms.TextBox();
this.button1.Location = new System.Drawing.Point(12, 18);
this.button1.Size = new System.Drawing.Size(119, 38);
this.button1.Text = "RemoveAt(0)";
this.button1.Click += new System.EventHandler(this.button1_Click);
this.textBox1.Location = new System.Drawing.Point(55, 75);
this.textBox1.ReadOnly = true;
this.textBox1.Size = new System.Drawing.Size(119, 20);
this.label1.Location = new System.Drawing.Point(12, 110);
this.label1.Size = new System.Drawing.Size(43, 14);
this.label1.Text = "Capital:";
this.label2.Location = new System.Drawing.Point(12, 78);
this.label2.Size = new System.Drawing.Size(34, 14);
this.label2.Text = "State:";
this.textBox2.Location = new System.Drawing.Point(55, 110);
this.textBox2.Size = new System.Drawing.Size(119, 20);
this.textBox2.ReadOnly = true;
this.ClientSize = new System.Drawing.Size(292, 273);
this.Controls.Add(this.textBox2);
this.Controls.Add(this.label2);
this.Controls.Add(this.label1);
this.Controls.Add(this.textBox1);
this.Controls.Add(this.button1);
this.Text = "Form1";
// Create an ArrayList containing some of the State objects.
states = new ArrayList();
states.Add(new State("California", "Sacramento"));
states.Add(new State("Oregon", "Salem"));
states.Add(new State("Washington", "Olympia"));
states.Add(new State("Idaho", "Boise"));
states.Add(new State("Utah", "Salt Lake City"));
states.Add(new State("Hawaii", "Honolulu"));
states.Add(new State("Colorado", "Denver"));
states.Add(new State("Montana", "Helena"));
bindingSource1 = new BindingSource();
// Bind BindingSource1 to the list of states.
bindingSource1.DataSource = states;
// Bind the two text boxes to properties of State.
textBox1.DataBindings.Add("Text", bindingSource1, "Name");
textBox2.DataBindings.Add("Text", bindingSource1, "Capital");
}
private void button1_Click(object sender, EventArgs e)
{
// If items remain in the list, remove the first item.
if (states.Count > 0)
{
states.RemoveAt(0);
// Call ResetBindings to update the textboxes.
bindingSource1.ResetBindings(false);
}
}
[STAThread]
static void Main()
{
Application.EnableVisualStyles();
Application.Run(new Form1());
}
// The State class to add to the ArrayList.
private class State
{
private string stateName;
public string Name
{
get {return stateName;}
}
private string stateCapital;
public string Capital
{
get {return stateCapital;}
}
public State ( string name, string capital)
{
stateName = name;
stateCapital = capital;
}
}
}
}
#using <System.Xml.dll>
#using <System.dll>
#using <System.Data.dll>
#using <System.Drawing.dll>
#using <System.Windows.Forms.dll>
using namespace System;
using namespace System::Collections::Generic;
using namespace System::ComponentModel;
using namespace System::Data;
using namespace System::Drawing;
using namespace System::Text;
using namespace System::Xml;
using namespace System::Windows::Forms;
using namespace System::IO;
namespace System_Windows_Forms_UpdateBinding
{
public ref class Form1: public Form
{
public:
Form1()
{
InitializeComponent();
}
[STAThread]
static void Main()
{
Application::EnableVisualStyles();
Application::Run( gcnew Form1 );
}
private:
void Form1_Load( System::Object^ /*sender*/, System::EventArgs^ /*e*/ )
{
// The xml to bind to.
String^ xml = "<US><states>" +
"<state><name>Washington</name><capital>Olympia</capital></state>" +
"<state><name>Oregon</name><capital>Salem</capital></state>" +
"<state><name>California</name><capital>Sacramento</capital></state>" +
"<state><name>Nevada</name><capital>Carson City</capital></state>" +
"</states></US>";
// Convert the xml string to bytes and load into a memory stream.
array<Byte>^ xmlBytes = Encoding::UTF8->GetBytes( xml );
MemoryStream^ stream = gcnew MemoryStream( xmlBytes,false );
// Create a DataSet and load the xml into it.
dataSet1->ReadXml( stream );
// Set the DataSource to the DataSet, and the DataMember
// to state.
bindingSource1->DataSource = dataSet1;
bindingSource1->DataMember = "state";
dataGridView1->DataSource = bindingSource1;
}
private:
void button1_Click( Object^ /*sender*/, EventArgs^ /*e*/ )
{
String^ xml = "<US><states>"
+ "<state><name>Washington</name><capital>Olympia</capital> "
+ "<flower>Coast Rhododendron</flower></state>"
+ "<state><name>Oregon</name><capital>Salem</capital>"
+ "<flower>Oregon Grape</flower></state>"
+ "<state><name>California</name><capital>Sacramento</capital>"
+ "<flower>California Poppy</flower></state>"
+ "<state><name>Nevada</name><capital>Carson City</capital>"
+ "<flower>Sagebrush</flower></state>"
+ "</states></US>";
// Convert the xml string to bytes and load into a memory stream.
array<Byte>^ xmlBytes = Encoding::UTF8->GetBytes( xml );
MemoryStream^ stream = gcnew MemoryStream( xmlBytes,false );
// Create a DataSet and load the xml into it.
dataSet2->ReadXml( stream );
// Set the data source.
bindingSource1->DataSource = dataSet2;
bindingSource1->ResetBindings( true );
}
System::Windows::Forms::Button^ button1;
System::Windows::Forms::DataGridView^ dataGridView1;
System::Windows::Forms::BindingSource^ bindingSource1;
System::Data::DataSet^ dataSet1;
DataSet^ dataSet2;
#pragma region Windows Form Designer generated code
/// <summary>
/// Required method for Designer support - do not modify
/// the contents of this method with the code editor.
/// </summary>
void InitializeComponent()
{
this->button1 = gcnew System::Windows::Forms::Button;
this->dataGridView1 = gcnew System::Windows::Forms::DataGridView;
this->bindingSource1 = gcnew System::Windows::Forms::BindingSource;
this->dataSet1 = gcnew System::Data::DataSet;
this->dataSet2 = gcnew System::Data::DataSet;
( (System::ComponentModel::ISupportInitialize^)(this->dataGridView1) )->BeginInit();
( (System::ComponentModel::ISupportInitialize^)(this->bindingSource1) )->BeginInit();
( (System::ComponentModel::ISupportInitialize^)(this->dataSet1) )->BeginInit();
( (System::ComponentModel::ISupportInitialize^)(this->dataSet2) )->BeginInit();
this->SuspendLayout();
//
// button1
//
this->button1->Location = System::Drawing::Point( 98, 222 );
this->button1->Name = "button1";
this->button1->TabIndex = 0;
this->button1->Text = "button1";
this->button1->Click += gcnew System::EventHandler( this, &Form1::button1_Click );
//
// dataGridView1
//
this->dataGridView1->Dock = System::Windows::Forms::DockStyle::Top;
this->dataGridView1->Location = System::Drawing::Point( 0, 0 );
this->dataGridView1->Name = "dataGridView1";
this->dataGridView1->Size = System::Drawing::Size( 292, 150 );
this->dataGridView1->TabIndex = 1;
//
// dataSet1
//
this->dataSet1->DataSetName = "NewDataSet";
this->dataSet1->Locale = gcnew System::Globalization::CultureInfo( "en-US" );
//
// dataSet2
//
this->dataSet2->DataSetName = "NewDataSet";
this->dataSet2->Locale = gcnew System::Globalization::CultureInfo( "en-US" );
//
// Form1
//
this->ClientSize = System::Drawing::Size( 292, 273 );
this->Controls->Add( this->dataGridView1 );
this->Controls->Add( this->button1 );
this->Name = "Form1";
this->Text = "Form1";
this->Load += gcnew EventHandler( this, &Form1::Form1_Load );
( (System::ComponentModel::ISupportInitialize^)(this->dataGridView1) )->EndInit();
( (System::ComponentModel::ISupportInitialize^)(this->bindingSource1) )->EndInit();
( (System::ComponentModel::ISupportInitialize^)(this->dataSet1) )->EndInit();
( (System::ComponentModel::ISupportInitialize^)(this->dataSet2) )->EndInit();
this->ResumeLayout( false );
}
#pragma endregion
};
}
int main()
{
System_Windows_Forms_UpdateBinding::Form1::Main();
}
Compilazione del codice
Per questo esempio sono necessari i seguenti requisiti:
- Riferimenti agli assembly System, System.Drawing e System.Windows.Forms.
Per informazioni sulla compilazione di questo esempio dalla riga di comando per Visual Basic o Visual C#, vedere Building from the Command Line (Visual Basic) o Compilazione dalla riga di comando con csc.exe. È anche possibile compilare questo esempio in Visual Studio incollando il codice in un nuovo progetto. Per ulteriori informazioni, vedere Procedura: compilare ed eseguire un esempio di codice Windows Form completo tramite Visual Studio e Procedura: compilare ed eseguire un esempio di codice Windows Form completo tramite Visual Studio e Procedura: compilare ed eseguire un esempio di codice Windows Form completo tramite Visual Studio e Procedura: compilare ed eseguire un esempio di codice Windows Form completo tramite Visual Studio e Procedura: compilare ed eseguire un esempio di codice Windows Form completo tramite Visual Studio.
Vedere anche
Attività
Procedura: associare un controllo Windows Form a un tipo