如何：對自訂物件實作驗證邏輯
此範例示範如何在自訂物件上實作驗證邏輯，然後繫結至它。
範例
如果您的來源物件實作 IDataErrorInfo，您可以在商業層提供驗證邏輯，如下列範例所示，它會定義實作 IDataErrorInfo 的 Person 物件：
public class Person : IDataErrorInfo
{
private int age;
public int Age
{
get { return age; }
set { age = value; }
}
public string Error
{
get
{
return null;
}
}
public string this[string name]
{
get
{
string result = null;
if (name == "Age")
{
if (this.age < 0 || this.age > 150)
{
result = "Age must not be less than 0 or greater than 150.";
}
}
return result;
}
}
}
Public Class Person
Implements IDataErrorInfo
Private _age As Integer
Public Property Age() As Integer
Get
Return _age
End Get
Set(ByVal value As Integer)
_age = value
End Set
End Property
Public ReadOnly Property [Error]() As String Implements IDataErrorInfo.Error
Get
Return Nothing
End Get
End Property
Default Public ReadOnly Property Item(ByVal columnName As String) As String Implements IDataErrorInfo.Item
Get
Dim result As String = Nothing
If columnName = "Age" Then
If Me._age < 0 OrElse Me._age > 150 Then
result = "Age must not be less than 0 or greater than 150."
End If
End If
Return result
End Get
End Property
End Class
在下列範例中，文字輸入框的文字屬性會繫結至 Person.Age 屬性，該屬性已透過提供給 x:Key data的資源宣告可繫結。 DataErrorValidationRule 會檢查 IDataErrorInfo 實作引發的驗證錯誤。
<Window x:Class="BusinessLayerValidation.Window1"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="WPF IDataErrorInfo Sample" Width="350" Height="150"
xmlns:src="clr-namespace:BusinessLayerValidation">
<Window.Resources>
<src:Person x:Key="data"/>
<!--The tool tip for the TextBox to display the validation error message.-->
<Style x:Key="textBoxInError" TargetType="TextBox">
<Style.Triggers>
<Trigger Property="Validation.HasError" Value="true">
<Setter Property="ToolTip"
Value="{Binding RelativeSource={x:Static RelativeSource.Self},
Path=(Validation.Errors)[0].ErrorContent}"/>
</Trigger>
</Style.Triggers>
</Style>
</Window.Resources>
<StackPanel Margin="20">
<TextBlock>Enter your age:</TextBlock>
<TextBox Style="{StaticResource textBoxInError}">
<TextBox.Text>
<!--By setting ValidatesOnExceptions to True, it checks for exceptions
that are thrown during the update of the source property.
An alternative syntax is to add <ExceptionValidationRule/> within
the <Binding.ValidationRules> section.-->
<Binding Path="Age" Source="{StaticResource data}"
ValidatesOnExceptions="True"
UpdateSourceTrigger="PropertyChanged">
<Binding.ValidationRules>
<!--DataErrorValidationRule checks for validation
errors raised by the IDataErrorInfo object.-->
<!--Alternatively, you can set ValidationOnDataErrors="True" on the Binding.-->
<DataErrorValidationRule/>
</Binding.ValidationRules>
</Binding>
</TextBox.Text>
</TextBox>
<TextBlock>Mouse-over to see the validation error message.</TextBlock>
</StackPanel>
</Window>
或者，除了使用 DataErrorValidationRule，您也可以將 ValidatesOnDataErrors 屬性設定為 true。
