使用带有 WPF & 的 DataAnnotations 验证数据实体框架? [英] Validate data using DataAnnotations with WPF & Entity Framework?

问题描述

有什么方法可以在 WPF & 中使用 DataAnnotations 进行验证?实体框架?

Is there any way to validate using DataAnnotations in WPF & Entity Framework?

推荐答案

您可以使用 DataAnnotations.Validator 类，如下所述:

You can use the DataAnnotations.Validator class, as described here:

http://johan.driessen.se/archive/2009/11/18/testing-dataannotation-based-validation-in-asp.net-mvc.aspx

但如果您对元数据使用伙伴"类，则需要在验证之前注册该事实，如下所述:

But if you're using a "buddy" class for the metadata, you need to register that fact before you validate, as described here:

http://forums.silverlight.net/forums/p/149264/377212.aspx

TypeDescriptor.AddProviderTransparent(
  new AssociatedMetadataTypeTypeDescriptionProvider(typeof(myEntity), 
    typeof(myEntityMetadataClass)), 
  typeof(myEntity));

List<ValidationResult> results = new List<ValidationResult>();
ValidationContext context = new ValidationContext(myEntity, null, null)
bool valid = Validator.TryValidateObject(myEntity, context, results, true);

[添加以下内容以回应 Shimmy 的评论]

我写了一个通用方法来实现上面的逻辑，这样任何对象都可以调用它:

I wrote a generic method to implement the logic above, so that any object can call it:

// If the class to be validated does not have a separate metadata class, pass
// the same type for both typeparams.
public static bool IsValid<T, U>(this T obj, ref Dictionary<string, string> errors)
{
    //If metadata class type has been passed in that's different from the class to be validated, register the association
    if (typeof(T) != typeof(U))
    {
        TypeDescriptor.AddProviderTransparent(new AssociatedMetadataTypeTypeDescriptionProvider(typeof(T), typeof(U)), typeof(T));
    }

    var validationContext = new ValidationContext(obj, null, null);
    var validationResults = new List<ValidationResult>();
    Validator.TryValidateObject(obj, validationContext, validationResults, true);

    if (validationResults.Count > 0 && errors == null)
        errors = new Dictionary<string, string>(validationResults.Count);

    foreach (var validationResult in validationResults)
    {
        errors.Add(validationResult.MemberNames.First(), validationResult.ErrorMessage);
    }

    if (validationResults.Count > 0)
        return false;
    else
        return true;
}

在每个需要验证的对象中，我添加了对这个方法的调用:

In each object that needs to be validated, I add a call to this method:

[MetadataType(typeof(Employee.Metadata))]
public partial class Employee
{
    private sealed class Metadata
    {
        [DisplayName("Email")]
        [Email(ErrorMessage = "Please enter a valid email address.")]
        public string EmailAddress { get; set; }
    }

    public bool IsValid(ref Dictionary<string, string> errors)
    {
        return this.IsValid<Employee, Metadata>(ref errors);
        //If the Employee class didn't have a buddy class,
        //I'd just pass Employee twice:
        //return this.IsValid<Employee, Employee>(ref errors);
    }
}

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