Cómo: Controlar errores y excepciones que se producen con el enlace de datos
Actualización: noviembre 2007
A menudo las excepciones y los errores aparecen en los objetos comerciales subyacentes cuando los enlaza a los controles. Puede interceptar estos errores y excepciones y, a continuación, recuperar o pasar al usuario la información de error controlando el evento BindingComplete para un componente Binding, BindingSource o CurrencyManager.
Ejemplo
Este ejemplo de código muestra cómo controlar los errores y excepciones que aparecen durante una operación de enlace de datos. Muestra cómo interceptar los errores controlando el evento Binding.BindingComplete de los objetos Binding. Para interceptar errores y excepciones controlando este evento, debe habilitar el formato para el enlace. Puede habilitar el formato cuando se crea o agrega un enlace a la colección de enlaces o estableciendo la propiedad FormattingEnabled en true.
Imports System
Imports System.Drawing
Imports System.Windows.Forms
Class Form1
Inherits Form
Private BindingSource1 As New BindingSource()
Private textBox1 As New TextBox()
Private textBox2 As New TextBox()
Private textBox3 As New TextBox()
Public Sub New()
'Set up the textbox controls.
Me.textBox1.Location = New System.Drawing.Point(82, 13)
Me.textBox1.TabIndex = 1
Me.textBox2.Location = New System.Drawing.Point(81, 47)
Me.textBox2.TabIndex = 2
Me.textBox3.Location = New System.Drawing.Point(81, 83)
Me.textBox3.TabIndex = 3
' Add the textbox controls to the form
Me.Controls.Add(Me.textBox2)
Me.Controls.Add(Me.textBox1)
Me.Controls.Add(Me.textBox3)
End Sub
Private WithEvents partNameBinding As Binding
Private WithEvents partNumberBinding As Binding
Private Sub Form1_Load(ByVal sender As Object, ByVal e As EventArgs) _
Handles Me.Load
' Set the DataSource of BindingSource1 to the Part type.
BindingSource1.DataSource = GetType(Part)
' Bind the textboxes to the properties of the Part type,
' enabling formatting.
partNameBinding = textBox1.DataBindings.Add("Text", BindingSource1, _
"PartName", True)
partNumberBinding = textBox2.DataBindings.Add("Text", BindingSource1, _
"PartNumber", True)
'Bind the textbox to the PartPrice value with currency formatting.
textBox3.DataBindings.Add("Text", BindingSource1, "PartPrice", _
True, DataSourceUpdateMode.OnPropertyChanged, 0, "C")
' Add a new part to BindingSource1.
BindingSource1.Add(New Part("Widget", 1234, 12.45))
End Sub
' Handle the BindingComplete event to catch errors and exceptions
' in binding process.
Sub partNumberBinding_BindingComplete(ByVal sender As Object, _
ByVal e As BindingCompleteEventArgs) _
Handles partNumberBinding.BindingComplete
If Not e.BindingCompleteState = BindingCompleteState.Success Then
MessageBox.Show("partNumberBinding: " + e.ErrorText)
End If
End Sub
' Handle the BindingComplete event to catch errors and exceptions
' in binding process.
Sub partNameBinding_BindingComplete(ByVal sender As Object, _
ByVal e As BindingCompleteEventArgs) _
Handles partNameBinding.BindingComplete
If Not e.BindingCompleteState = BindingCompleteState.Success Then
MessageBox.Show("partNameBinding: " + e.ErrorText)
End If
End Sub
<STAThread()> _
Shared Sub Main()
Application.EnableVisualStyles()
Application.Run(New Form1())
End Sub
End Class
' Represents a business object that throws exceptions when invalid
' values are entered for some of its properties.
Public Class Part
Private name As String
Private number As Integer
Private price As Double
Public Sub New(ByVal name As String, ByVal number As Integer, _
ByVal price As Double)
PartName = name
PartNumber = number
PartPrice = price
End Sub
Public Property PartName() As String
Get
Return name
End Get
Set(ByVal value As String)
If Value.Length <= 0 Then
Throw New Exception("Each part must have a name.")
Else
name = Value
End If
End Set
End Property
Public Property PartPrice() As Double
Get
Return price
End Get
Set(ByVal value As Double)
price = Value
End Set
End Property
Public Property PartNumber() As Integer
Get
Return number
End Get
Set(ByVal value As Integer)
If Value < 100 Then
Throw New Exception("Invalid part number." _
& " Part numbers must be greater than 100.")
Else
number = Value
End If
End Set
End Property
End Class
using System;
using System.Drawing;
using System.Windows.Forms;
class Form1 : Form
{
private BindingSource BindingSource1 = new BindingSource();
private TextBox textBox1 = new TextBox();
private TextBox textBox2 = new TextBox();
private TextBox textBox3 = new TextBox();
public Form1()
{
//Set up the textbox controls.
this.textBox1.Location = new System.Drawing.Point(82, 13);
this.textBox1.TabIndex = 1;
this.textBox2.Location = new System.Drawing.Point(81, 47);
this.textBox2.TabIndex = 2;
this.textBox3.Location = new System.Drawing.Point(81, 83);
this.textBox3.TabIndex = 3;
// Add the textbox controls to the form
this.Controls.Add(this.textBox2);
this.Controls.Add(this.textBox1);
this.Controls.Add(this.textBox3);
// Handle the form's Load event.
this.Load += new System.EventHandler(this.Form1_Load);
}
Binding partNameBinding;
Binding partNumberBinding;
private void Form1_Load(object sender, EventArgs e)
{
// Set the DataSource of BindingSource1 to the Part type.
BindingSource1.DataSource = typeof(Part);
// Bind the textboxes to the properties of the Part type,
// enabling formatting.
partNameBinding = textBox1.DataBindings.Add("Text",
BindingSource1, "PartName", true);
partNumberBinding = textBox2.DataBindings.Add("Text", BindingSource1, "PartNumber",
true);
//Bind the textbox to the PartPrice value with currency formatting.
textBox3.DataBindings.Add("Text", BindingSource1, "PartPrice", true,
DataSourceUpdateMode.OnPropertyChanged, 0, "C");
// Handle the BindingComplete event for BindingSource1 and
// the partNameBinding.
partNumberBinding.BindingComplete +=
new BindingCompleteEventHandler(partNumberBinding_BindingComplete);
partNameBinding.BindingComplete +=
new BindingCompleteEventHandler(partNameBinding_BindingComplete);
// Add a new part to BindingSource1.
BindingSource1.Add(new Part("Widget", 1234, 12.45));
}
// Handle the BindingComplete event to catch errors and exceptions
// in binding process.
void partNumberBinding_BindingComplete(object sender,
BindingCompleteEventArgs e)
{
if (e.BindingCompleteState != BindingCompleteState.Success)
MessageBox.Show("partNumberBinding: " + e.ErrorText);
}
// Handle the BindingComplete event to catch errors and
// exceptions in binding process.
void partNameBinding_BindingComplete(object sender,
BindingCompleteEventArgs e)
{
if (e.BindingCompleteState != BindingCompleteState.Success)
MessageBox.Show("partNameBinding: " + e.ErrorText);
}
[STAThread]
static void Main()
{
Application.EnableVisualStyles();
Application.Run(new Form1());
}
}
// Represents a business object that throws exceptions when invalid values are
// entered for some of its properties.
public class Part
{
private string name;
private int number;
private double price;
public Part(string name, int number, double price)
{
PartName = name;
PartNumber = number;
PartPrice = price;
}
public string PartName
{
get { return name; }
set
{
if (value.Length <= 0)
throw new Exception("Each part must have a name.");
else
name = value;
}
}
public double PartPrice
{
get { return price; }
set { price = value; }
}
public int PartNumber
{
get { return number; }
set
{
if (value < 100)
throw new Exception("Invalid part number." +
" Part numbers must be greater than 100.");
else
number = value;
}
}
}
// Represents a business object that throws exceptions when
// invalid values are entered for some of its properties.
public ref class Part
{
private:
String^ name;
int number;
double price;
public:
Part(String^ name, int number, double price)
{
PartName = name;
PartNumber = number;
PartPrice = price;
}
property String^ PartName
{
String^ get()
{
return name;
}
void set(String^ value)
{
if (value->Length <= 0)
{
throw gcnew Exception(
"Each part must have a name.");
}
else
{
name = value;
}
}
}
property double PartPrice
{
double get()
{
return price;
}
void set(double value)
{
price = value;
}
}
property int PartNumber
{
int get()
{
return number;
}
void set(int value)
{
if (value < 100)
{
throw gcnew Exception(
"Invalid part number." \
"Part numbers must be " \
"greater than 100.");
}
else
{
number = value;
}
}
}
};
ref class MainForm: public Form
{
private:
BindingSource^ bindingSource;
TextBox^ partNameTextBox;
TextBox^ partNumberTextBox;
TextBox^ partPriceTextBox;
public:
MainForm()
{
bindingSource = gcnew BindingSource;
partNameTextBox = gcnew TextBox;
partNumberTextBox = gcnew TextBox;
partPriceTextBox = gcnew TextBox;
//Set up the textbox controls.
this->partNameTextBox->Location = Point(82, 13);
this->partNameTextBox->TabIndex = 1;
this->partNumberTextBox->Location = Point(81, 47);
this->partNumberTextBox->TabIndex = 2;
this->partPriceTextBox->Location = Point(81, 83);
this->partPriceTextBox->TabIndex = 3;
// Add the textbox controls to the form
this->Controls->Add(this->partNumberTextBox);
this->Controls->Add(this->partNameTextBox);
this->Controls->Add(this->partPriceTextBox);
// Handle the form's Load event.
this->Load += gcnew EventHandler(this,
&MainForm::OnMainFormLoad);
}
private:
void OnMainFormLoad(Object^ sender, EventArgs^ e)
{
// Set the DataSource of bindingSource to the Part type.
bindingSource->DataSource = Part::typeid;
// Bind the textboxes to the properties of the Part type,
// enabling formatting.
partNameTextBox->DataBindings->Add(
"Text", bindingSource, "PartName", true);
partNumberTextBox->DataBindings->Add(
"Text", bindingSource, "PartNumber", true);
//Bind the textbox to the PartPrice value
// with currency formatting.
partPriceTextBox->DataBindings->Add("Text", bindingSource, "PartPrice", true,
DataSourceUpdateMode::OnPropertyChanged, nullptr, "C");
// Handle the BindingComplete event for bindingSource and
// the partNameBinding.
bindingSource->BindingComplete +=
gcnew BindingCompleteEventHandler(this,
&MainForm::OnBindingSourceBindingComplete);
bindingSource->BindingComplete +=
gcnew BindingCompleteEventHandler(this,
&MainForm::OnPartNameBindingBindingComplete);
// Add a new part to bindingSource.
bindingSource->Add(gcnew Part("Widget", 1234, 12.45));
}
// Handle the BindingComplete event to catch errors and
// exceptions in binding process.
void OnBindingSourceBindingComplete(Object^ sender,
BindingCompleteEventArgs^ e)
{
if (e->BindingCompleteState ==
BindingCompleteState::Exception)
{
MessageBox::Show(String::Format(
CultureInfo::CurrentCulture,
"bindingSource: {0}", e->Exception->Message));
}
if (e->BindingCompleteState ==
BindingCompleteState::DataError)
{
MessageBox::Show(String::Format(
CultureInfo::CurrentCulture,
"bindingSource: {0}", e->Exception->Message));
}
}
// Handle the BindingComplete event to catch errors and
// exceptions in binding process.
void OnPartNameBindingBindingComplete(Object^ sender,
BindingCompleteEventArgs^ e)
{
if (e->BindingCompleteState ==
BindingCompleteState::Exception)
{
MessageBox::Show(String::Format(
CultureInfo::CurrentCulture,
"PartNameBinding: {0}", e->Exception->Message));
}
if (e->BindingCompleteState ==
BindingCompleteState::DataError)
{
MessageBox::Show(String::Format(
CultureInfo::CurrentCulture,
"PartNameBinding: {0}", e->Exception->Message));
}
}
};
Mientras se ejecuta el código y se especifica una cadena vacía para el nombre de la pieza o un valor inferior a 100 para el nombre de la pieza, aparece un cuadro de mensaje. Éste es el resultado de controlar el evento Binding.BindingComplete para estos enlaces del cuadro de texto.
Compilar el código
Este ejemplo requiere:
- Referencias a los ensamblados System, System.Drawing y System.Windows.Forms.
Para obtener información sobre la generación de este ejemplo desde la línea de comandos de Visual Basic o Visual C#, vea Generar desde la línea de comandos (Visual Basic) o Generar la línea de comandos con csc.exe. También puede generar este ejemplo en Visual Studio pegando el código en un proyecto nuevo.