我开始通过IDataErrorInfo接口在我的
WPF项目中实现验证.
我的业务对象包含多个具有验证信息的属性.如何获取与该对象相关联的所有错误消息的列表.我的想法是,这是什么Error属性,但我无法追踪任何人使用此报告多个属性.
我的业务对象包含多个具有验证信息的属性.如何获取与该对象相关联的所有错误消息的列表.我的想法是,这是什么Error属性,但我无法追踪任何人使用此报告多个属性.
谢谢！
public string this[string property]
{
get {
string msg = null;
switch (property)
{
case "LastName":
if (string.IsNullOrEmpty(LastName))
msg = "Need a last name";
break;
case "FirstName":
if (string.IsNullOrEmpty(LastName))
msg = "Need a first name";
break;
default:
throw new ArgumentException(
"Unrecognized property: " + property);
}
return msg;
}
}
public string Error
{
get
{
return null ;
}
}
解决方法
我认为使用验证属性要容易得多.
class MyBusinessObject {
[required(ErrorMessage="Must enter customer")]
public string Customer { get; set; }
[Range(10,99,ErrorMessage="Price must be between 10 and 99")]
public decimal Price { get; set; }
// I have also created some custom attributes,e.g. validate paths
[File(FileValidation.IsDirectory,ErrorMessage = "Must enter an importfolder")]
public string ImportFolder { get; set; }
public string this[string columnName] {
return InputValidation<MyBusinessObject>.Validate(this,columnName);
}
public ICollection<string> AllErrors() {
return InputValidation<MyBusinessObject>.Validate(this);
}
}
辅助类InputValidation看起来像这样
internal static class InputValidation<T>
where T : IDataErrorInfo
{
/// <summary>
/// Validate a single column in the source
/// </summary>
/// <remarks>
/// Usually called from IErrorDataInfo.this[]</remarks>
/// <param name="source">Instance to validate</param>
/// <param name="columnName">Name of column to validate</param>
/// <returns>Error messages separated by newline or string.Empty if no errors</returns>
public static string Validate(T source,string columnName) {
KeyValuePair<Func<T,object>,ValidationAttribute[]> validators;
if (mAllValidators.TryGetValue(columnName,out validators)) {
var value = validators.Key(source);
var errors = validators.Value.Where(v => !v.IsValid(value)).Select(v => v.ErrorMessage ?? "").ToArray();
return string.Join(Environment.NewLine,errors);
}
return string.Empty;
}
/// <summary>
/// Validate all columns in the source
/// </summary>
/// <param name="source">Instance to validate</param>
/// <returns>List of all error messages. Empty list if no errors</returns>
public static ICollection<string> Validate(T source) {
List<string> messages = new List<string>();
foreach (var validators in mAllValidators.Values) {
var value = validators.Key(source);
messages.AddRange(validators.Value.Where(v => !v.IsValid(value)).Select(v => v.ErrorMessage ?? ""));
}
return messages;
}
/// <summary>
/// Get all validation attributes on a property
/// </summary>
/// <param name="property"></param>
/// <returns></returns>
private static ValidationAttribute[] GetValidations(PropertyInfo property) {
return (ValidationAttribute[])property.GetCustomAttributes(typeof(ValidationAttribute),true);
}
/// <summary>
/// Create a lambda to receive a property value
/// </summary>
/// <param name="property"></param>
/// <returns></returns>
private static Func<T,object> CreateValueGetter(PropertyInfo property) {
var instance = Expression.Parameter(typeof(T),"i");
var cast = Expression.TypeAs(Expression.Property(instance,property),typeof(object));
return (Func<T,object>)Expression.Lambda(cast,instance).Compile();
}
private static readonly Dictionary<string,KeyValuePair<Func<T,ValidationAttribute[]>> mAllValidators;
static InputValidation() {
mAllValidators = new Dictionary<string,ValidationAttribute[]>>();
foreach (var property in typeof(T).GetProperties()) {
var validations = GetValidations(property);
if (validations.Length > 0)
mAllValidators.Add(property.Name,new KeyValuePair<Func<T,ValidationAttribute[]>(
CreateValueGetter(property),validations));
}
}
}
