在MVC3中使用强类型视图时可能的模型继承？

Question

我的模型中有以下设置:

namespace QuickTest.Models
{
    public class Person
    {
        [Required]
        [Display(Name = "Full name")]
        public string FullName { get; set; }

        [Display(Name = "Address Line 1")]
        public virtual string Address1 { get; set; }
    }
    public class Sender : Person
    {
        [Required]
        public override string Address1 { get; set; }
    }
    public class Receiver : Person
    {
    }
}

在我看来:

@model QuickTest.Models.Person
@{
    ViewBag.Title = "Edit";
}
<script src="@Url.Content("~/Scripts/jquery.validate.min.js")" type="text/javascript"></script>
<script src="@Url.Content("~/Scripts/jquery.validate.unobtrusive.min.js")" type="text/javascript"></script>

@using (Html.BeginForm()) {
    <fieldset>
        <legend>Person</legend>
        <div class="editor-label">
            @Html.LabelFor(model => model.FullName)
        </div>
        <div class="editor-field">
            @Html.EditorFor(model => model.FullName)
            @Html.ValidationMessageFor(model => model.FullName)
        </div>
        <div class="editor-label">
            @Html.LabelFor(model => model.Address1)
        </div>
        <div class="editor-field">
            @Html.EditorFor(model => model.Address1)
            @Html.ValidationMessageFor(model => model.Address1)
        </div>

        <div class="errors">
            @Html.ValidationSummary(true)
        </div>
        <p>
            <input type="submit" value="Save" />
        </p>
    </fieldset>
}

启用客户端验证.但是,如果我将一个Sender类型的对象发送到View,则客户端验证不会检测到需要Address1字段.有没有办法让客户端验证在这种情况下工作？

PS:我发现如果我使用以下内容在视图中显示Address1字段,则客户端验证有效:

<div class="editor-field">
    @Html.Editor("Address1", Model.Address1)
    @Html.ValidationMessageFor(model => model.Address1)
</div>

Answer 1

您可以自定义验证器和元数据来自您的具体类,但该解决方案有几个移动部件,包括两个自定义元数据提供程序.

首先,创建一个自定义Attribute来装饰基类的每个属性.这对于我们的自定义提供程序来说是必需的,以指示何时需要进一步分析.这是属性:

[AttributeUsage(AttributeTargets.All, Inherited = true, AllowMultiple = true)]
public class BaseTypeAttribute : Attribute { }

接下来,创建一个ModelMetadataProvider继承自的自定义DataAnnotationsModelMetadataProvider:

public class MyModelMetadataProvider : DataAnnotationsModelMetadataProvider
{
    protected override ModelMetadata CreateMetadata(
        IEnumerable<Attribute> attributes,
        Type containerType,
        Func<object> modelAccessor,
        Type modelType,
        string propertyName)
    {
        var attribute = attributes.FirstOrDefault(a => a.GetType().Equals(typeof(BaseTypeAttribute))) as BaseTypeAttribute;
        if (attribute != null && modelAccessor != null)
        {
            var target = modelAccessor.Target;
            var containerField = target.GetType().GetField("container");
            if (containerField == null)
            {
                var vdi = target.GetType().GetField("vdi").GetValue(target) as ViewDataInfo;
                var concreteType = vdi.Container.GetType();
                return base.CreateMetadata(attributes, concreteType, modelAccessor, modelType, propertyName);
            }
            else
            {
                var container = containerField.GetValue(target);
                var concreteType = container.GetType();
                var propertyField = target.GetType().GetField("property");
                if (propertyField == null)
                {
                    concreteType = base.GetMetadataForProperties(container, containerType)
                        .FirstOrDefault(p => p.PropertyName == "ConcreteType").Model as System.Type;
                    if (concreteType != null)
                        return base.GetMetadataForProperties(container, concreteType)
                            .FirstOrDefault(pr => pr.PropertyName == propertyName);
                }
                return base.CreateMetadata(attributes, concreteType, modelAccessor, modelType, propertyName);
            }
        }
        return base.CreateMetadata(attributes, containerType, modelAccessor, modelType, propertyName);
    }
}

然后,创建一个ModelValidatorProvider继承自的自定义DataAnnotationsModelValidatorProvider:

public class MyModelMetadataValidatorProvider : DataAnnotationsModelValidatorProvider
{
    protected override IEnumerable<ModelValidator> GetValidators(ModelMetadata metadata, ControllerContext context, IEnumerable<Attribute> attributes)
    {
        List<ModelValidator> vals = base.GetValidators(metadata, context, attributes).ToList();

        var baseTypeAttribute = attributes.FirstOrDefault(a => a.GetType().Equals(typeof(BaseTypeAttribute))) 
            as BaseTypeAttribute;

        if (baseTypeAttribute != null)
        {
            // get our parent model
            var parentMetaData = ModelMetadataProviders.Current.GetMetadataForProperties(context.Controller.ViewData.Model,
                metadata.ContainerType);

            // get the concrete type
            var concreteType = parentMetaData.FirstOrDefault(p => p.PropertyName == "ConcreteType").Model;
            if (concreteType != null)
            {
                var concreteMetadata = ModelMetadataProviders.Current.GetMetadataForProperties(context.Controller.ViewData.Model,
                    Type.GetType(concreteType.ToString()));

                var concretePropertyMetadata = concreteMetadata.FirstOrDefault(p => p.PropertyName == metadata.PropertyName);

                vals = base.GetValidators(concretePropertyMetadata, context, attributes).ToList();
            }
        }
        return vals.AsEnumerable();
    }
}

之后,Application_Start在Global.asax.cs中注册两个自定义提供程序:

ModelValidatorProviders.Providers.Clear();
ModelValidatorProviders.Providers.Add(new MvcApplication8.Controllers.MyModelMetadataValidatorProvider());
ModelMetadataProviders.Current = new MvcApplication8.Controllers.MyModelMetadataProvider();

现在,改变你的模型:

public class Person
{
    public Type ConcreteType { get; set; }

    [Required]
    [Display(Name = "Full name")]
    [BaseType]
    public string FullName { get; set; }

    [Display(Name = "Address Line 1")]
    [BaseType]
    public virtual string Address1 { get; set; }
}

public class Sender : Person
{
    public Sender()
    {
        this.ConcreteType = typeof(Sender);
    }

    [Required]
    [Display(Name = "Address Line One")]
    public override string Address1 { get; set; }
}

public class Receiver : Person
{
}

请注意,基类具有新属性ConcreteType.这将用于指示哪个继承类已实例化此基类.每当继承类具有覆盖基类中元数据的元数据时,继承类的构造函数应该设置基类ConcreteType属性.

现在,即使您的视图使用基类,特定于任何具体继承类的属性也将出现在您的视图中,并将影响模型的验证.

此外,您应该能够将View转换为Person类型的模板,并将该模板用于使用基类的任何实例或从中继承.