Procedimiento para controlar errores y excepciones que se producen con el enlace de datos

A menudo, las excepciones y los errores se producen en los objetos comerciales subyacentes cuando se enlazan a controles. Puede interceptar estos errores y excepciones y, después, recuperar o pasar la información de error al usuario controlando el evento BindingComplete para un componente Binding, BindingSource o CurrencyManager determinado.

Ejemplo

En este ejemplo de código se muestra cómo controlar errores y excepciones que se producen 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 del enlace. Puede habilitar el formato al crear el enlace o al agregarlo a la colección de enlaces, o estableciendo la propiedad FormattingEnabled en true.

// 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));
        }
    }
};

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;
        }
    }
}

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

Cuando se ejecuta el código y se especifica una cadena vacía como nombre de elemento o un valor inferior a 100 como número de elemento, aparece un cuadro de mensaje. Este es el resultado de controlar el evento Binding.BindingComplete para estos enlaces de cuadro de texto.

Compilar el código

Para este ejemplo se necesita:

• Referencias a los ensamblados System, System.Drawing y System.Windows.Forms.

Vea también

• Binding.BindingComplete
• BindingSource.BindingComplete
• Componente BindingSource