HOW TO：處理資料繫結時所發生的錯誤和例外狀況
當您將基礎商務物件 (Business Object) 繫結至控制項時，這個物件常常會發生例外狀況和錯誤。 藉由處理特定 Binding、BindingSource 或 CurrencyManager 元件的 BindingComplete 事件，可以攔截這些錯誤和例外狀況，然後選擇進行修復或將錯誤資訊傳遞給使用者。
範例
這個程式碼範例示範如何處理在資料繫結作業期間所發生的錯誤和例外狀況。 它示範如何藉由處理 Binding 物件的 Binding.BindingComplete 事件來攔截錯誤。 必須啟用繫結格式設定，才能藉由處理這個事件來攔截錯誤。 當繫結集合中建構入或加入繫結時，即可啟用格式設定，或者也可以藉由將 FormattingEnabled 屬性設為 true 來啟用。
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));
}
}
};
當程式碼正在執行時，如果零件名稱輸入了空字串或者零件編號輸入了小於 100 的值，則會出現訊息方塊。 這是處理這些文字方塊繫結的 Binding.BindingComplete 事件所得的結果。
編譯程式碼
這個範例需要：
- System、System.Drawing 和 System.Windows.Forms 組件的參考。
如需從 Visual Basic 或 Visual C# 的命令列建置這個範例的詳細資訊，請參閱從命令列建置 (Visual Basic) 或使用 csc.exe 建置命令列。 您也可以透過將程式碼貼入新的專案，在 Visual Studio 中建置此範例。 如需詳細資訊，請參閱HOW TO：使用 Visual Studio 編譯及執行完整的 Windows Form 程式碼範例 和 HOW TO：使用 Visual Studio 編譯及執行完整的 Windows Form 程式碼範例 和 HOW TO：使用 Visual Studio 編譯及執行完整的 Windows Form 程式碼範例 和 HOW TO：使用 Visual Studio 編譯及執行完整的 Windows Form 程式碼範例 和 如何：使用 Visual Studio 編譯及執行完整的 Windows Form 程式碼範例.