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　　binding是一个非常重要的特性，所有的验证显示也都是通过它来实现的。在Silverlight4中由IDataErrorInfo and INotifyDataErrorInfo interfaces 来实现。

1 捕获异常

<TextBox Grid.Row="0" Grid.Column="1"
Text="{Binding LastName, Mode=TwoWay,
ValidatesOnExceptions=True}" />

　public string LastName
{
get { return _lastName; }
set
{
if (string.IsNullOrEmpty(value))
throw new Exception("姓不能为空");
_lastName = value;
NotifyPropertyChanged("LastName");
}

2、使用INotifyPropertyChanged, IDataErrorInfo 验证和显示

public class Employee : INotifyPropertyChanged, IDataErrorInfo {
private string _lastName;
public string LastName {
get { return _lastName; }
set {
if (string.IsNullOrEmpty(value))
_dataErrors["LastName"] = "Last Name is required";
else if (value.Trim().Length < 2)
_dataErrors["LastName"] =
"Last Name must be at least 2 letters long.";
else
if (_dataErrors.ContainsKey("LastName"))
_dataErrors.Remove("LastName");

　　 _lastName = value;
NotifyPropertyChanged("LastName");
}
}

　#region IDataErrorInfo Members

　 private string _dataError = string.Empty;

　 public string Error {
get { return _dataError; }
}

　 private Dictionary<string, string> _dataErrors =
new Dictionary<string, string>();

　public string this[string columnName] {
get {
if (_dataErrors.ContainsKey(columnName))
return _dataErrors[columnName];
else
return null;
}
}

　}

　xaml 中

　<TextBox Grid.Row="0"
Grid.Column="1"
 Text="{Binding LastName, Mode=TwoWay, ValidatesOnDataErrors=True}" />

3、异常验证INotifyDataErrorInfo

IEnumerable INotifyDataErrorInfo.GetErrors(string propertyName)
{
if (!string.IsNullOrEmpty(propertyName))
{
if (_validationErrors.ContainsKey(propertyName))
return _validationErrors[propertyName];
else
return null;
}
else
{
return _classValidationErrors;
}
}

　bool INotifyDataErrorInfo.HasErrors
{
get
{
if (_classValidationErrors.Count > 0)
return true;

　foreach (string key in _validationErrors.Keys)
{
if (_validationErrors[key].Count > 0)
return true;
}

return false;
}
}

　 #endregion

4、为你的实体类添加属性

[Required]
[StringLength(320)]
[RegularExpression(@"^[a-zA-Z][\w\.&-]*[a-zA-Z0-9]@[a-zA-Z0-9]
[\w\.-]*[a-zA-Z0-9]\.[a-zA-Z\.]*[a-zA-Z]$")]
public string EmailAddress { get; set; }
[Range(0, 20)]
public int NumberOfChildren { get; set; }

还可以自定义

方法1

public class CustomValidationMethods
{
public static ValidationResult NameBeginsWithB(string name)
{
if (name.StartsWith("B"))
return ValidationResult.Success;
else
return new ValidationResult("Name does not begin with 'B'");
}
}

[CustomValidation(typeof(CustomValidationMethods),
"NameBeginsWithB"]
public string LastName { get; set; }

方法2

public class NameBeginsWithBAttribute : ValidationAttribute
{
protected override ValidationResult IsValid(
object value, ValidationContext validationContext)
{
if (!(value is string))
return new ValidationResult(
"Incorrect data type. Expected string");
if (string.IsNullOrEmpty((string)value))
return ValidationResult.Success;
if (((string)value).StartsWith("B"))
return ValidationResult.Success;
else
return new ValidationResult(
string.Format("{0} does not begin with 'B'",
validationContext.DisplayName));
}
}