将数据注释添加到通过DLL引用提供的类中，该引用由多个应用程序共享

Question

In my application I am using a class that is supplied by external library, and used across multiple applications. I would like to add Data Annotations to the properties of this class, but it must be contained within my application.

I've produced the following code that will retrieve all attributes for a property, but cannot find a way to add a Data Annotation attribute. Lets say I have a class called vehicle that has a property of VIN:

AttributeCollection oldAttributeCollection = TypeDescriptor.GetProperties(instance).Find("VIN", true).Attributes;

Answer 1

The short answer is you can't add attributes to a class dynamically. For more info see this related question

Answer 2

I found the solution. The method below will execute for each property in the current model. I am able to apply some logic and determine if I want to add my custom "ConditionallyRequired" Data Annotation to the property.

  public class CustomMetadataValidationProvider : DataAnnotationsModelValidatorProvider
    {
        protected override IEnumerable<ModelValidator> GetValidators(ModelMetadata metadata, ControllerContext context, IEnumerable<Attribute> attributes)
        {
            var validators = PermissionManager.Settings.Validation.ToList();
            var validateField =
                validators.SingleOrDefault(v => v.FieldName == metadata.PropertyName && v.IsValidated == "True");

            var attr = new List<Attribute>();
            attr.AddRange(attributes);
            if (validateField != null)
            {

                attr.Add(new ConditionallyRequired(validateField.FieldName));
            }
            return base.GetValidators(metadata, context, attr);
        }
    }

Then initialize the CustomMetadataValidationProvider class in the global.asax like so:

protected void Application_Start()
    {
        ModelValidatorProviders.Providers.Add(new ConditionallyRequired.CustomMetadataValidationProvider());
        AreaRegistration.RegisterAllAreas();

    }

Answer 3

右键单击您的类库，然后选择“管理NuGet程序包...”，然后在“浏览”选项卡->中：System.ComponentModel.DataAnnotations并安装