13

我希望能够从 cookie 中获取键/值并使用它来绑定模型。

我相信 DefaultModelBinder 开箱即用，而不是构建自定义 ModelBinder，而且选择值来自何处的最佳方法是设置它使用的 IValueProvider。

为此，我不想创建自定义 ValueProviderFactory 并将其绑定到全局，因为我只想将此 ValueProvider 用于特定的操作方法。

我已经建立了一个执行此操作的属性：

/// <summary>
/// Replaces the current value provider with the specified value provider
/// </summary>
[AttributeUsage(AttributeTargets.Method | AttributeTargets.Class, Inherited = true, AllowMultiple = true)]
public class SetValueProviderAttribute : ActionFilterAttribute
{
    public SetValueProviderAttribute(Type valueProviderType)
    {
        if (valueProviderType.GetInterface(typeof(IValueProvider).Name) == null)
            throw new ArgumentException("Type " + valueProviderType + " must implement interface IValueProvider.", "valueProviderType");

        _ValueProviderType = valueProviderType;
    }

    private Type _ValueProviderType;

    public override void OnActionExecuting(ActionExecutingContext filterContext)
    {
        IValueProvider valueProviderToAdd = GetValueProviderToAdd();

        filterContext.Controller.ValueProvider = valueProviderToAdd;
    }

    private IValueProvider GetValueProviderToAdd()
    {
        return (IValueProvider)Activator.CreateInstance(_ValueProviderType);
    }
}

不幸的是，ModelBinder 及其 IValueProvider 是在 OnActionExecuting 之前设置的（为什么？？？？？？）。有没有其他人想出一种在不使用 ValueProviderFactory 的情况下将自定义 IValueProvider 注入 DefaultModelBinder 的方法？

4

3 回答 3

10

ValueProviderFactory在这种情况下，您仍应使用 a 。

您必须在您的方法上实现的方法ValueProviderFactory具有以下签名：

IValueProvider GetValueProvider(ControllerContext controllerContext)

在该方法的实现中，您可以检查控制器上下文，如果传入请求是针对您想要利用 cookie 的控制器/操作，则返回 some CustomCookieValueProvider.

如果您不想为请求使用 cookie，只需返回null，框架就会将其从值提供者列表中过滤掉。

作为奖励，您可能不想将何时使用的逻辑硬编码CustomCookieValueProvider到ValueProviderFactory. 也许，您可以利用DataTokens给定路由匹配何时使用 cookie。所以添加这样的路线：

routes.MapRoute("SomeRoute","{controller}/{action}").DataTokens.Add("UseCookies", true);

注意DataTokens.Add()那里的调用，现在在你的GetValueProvider方法中你可以做这样的事情：

if (controllerContext.RouteData.DataTokens.ContainsKey("UseCookies"))
{
    return new CustomCookieValueProvider(controllerContext.RequestContext.HttpContext.Request.Cookies);
}

return null;
于 2011-10-07T14:59:07.790 回答
4

这是一种替代方法，可让您将 IValueProviders 指定为针对操作参数的属性。这使得 IValueProviders 是瞬态的，而不是全局的。

public interface IControllerContextAware
{
    ControllerContext ControllerContext { get; set; }
}

[AttributeUsage(AttributeTargets.Class | AttributeTargets.Struct | AttributeTargets.Enum | AttributeTargets.Interface | AttributeTargets.Parameter, AllowMultiple = false, Inherited = false)]
public class ValueProviderAttribute : CustomModelBinderAttribute
{
    public Type[] ValueProviders { get; private set; }

    public ValueProviderAttribute(params Type[] valueProviders)
    {
        if (valueProviders == null)
        {
            throw new ArgumentNullException("valueProviders");
        }
        foreach (var valueProvider in valueProviders.Where(valueProvider => !typeof(IValueProvider).IsAssignableFrom(valueProvider)))
        {
            throw new ArgumentException(string.Format(CultureInfo.CurrentCulture, "The valueProvider {0} must be of type {1}", valueProvider.FullName, typeof(IValueProvider)), "valueProviders");
        }

        ValueProviders = valueProviders;
    }

    public override IModelBinder GetBinder()
    {
        return new ValueProviderModelBinder
            {
                ValueProviderTypes = ValueProviders.ToList(),
                CreateValueProvider = OnCreateValueProvider
            };
    }

    protected virtual IValueProvider OnCreateValueProvider(Type valueProviderType, ControllerContext controllerContext, ModelBindingContext bindingContext)
    {
        var valueProvider = (IValueProvider)Activator.CreateInstance(valueProviderType);
        if (valueProvider is IControllerContextAware)
        {
            (valueProvider as IControllerContextAware).ControllerContext = controllerContext;
        }
        return valueProvider;
    }

    private class ValueProviderModelBinder : DefaultModelBinder
    {
        public IList<Type> ValueProviderTypes { get; set; }
        public Func<Type, ControllerContext, ModelBindingContext, IValueProvider> CreateValueProvider { get; set; }

        public override object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
        {
            var valueProviders = from type in ValueProviderTypes
                                 select CreateValueProvider(type, controllerContext, bindingContext);

            bindingContext.ValueProvider = new ValueProviderCollection(valueProviders.Concat((Collection<IValueProvider>)bindingContext.ValueProvider).ToList());

            return base.BindModel(controllerContext, bindingContext);
        }
    }
}

这基本上是 ModelBinderAttribute 的代码，但有一些调整。它不是密封的，因此您可以根据需要更改创建 IValueProvider 的方式。

这是一个简单的示例，它查看另一个字段，可能是隐藏或加密的字段，然后获取数据并将其放入另一个属性中。

这是模型，它不知道 IValueProvider，但知道隐藏字段。

public class SomeModel
{
    [Required]
    public string MyString { get; set; }

    [Required]
    public string MyOtherString { get; set; }

    [Required]
    public string Data { get; set; }
}

然后我们有 IValueProvider，在这种情况下，我的提供者明确知道我的模型，但不一定是这种情况。

public class MyValueProvider : IValueProvider, IControllerContextAware
{
    public ControllerContext ControllerContext { get; set; }

    public bool ContainsPrefix(string prefix)
    {
        var containsPrefix = prefix == "MyString" && ControllerContext.HttpContext.Request.Params.AllKeys.Any(key => key == "Data");
        return containsPrefix;
    }

    public ValueProviderResult GetValue(string key)
    {
        if (key == "MyString")
        {
            var data = ControllerContext.RequestContext.HttpContext.Request.Params["Data"];

            var myString = data.Split(':')[1];

            return new ValueProviderResult(myString, myString, CultureInfo.CurrentCulture);
        }
        return null;
    }
}

然后是把这一切联系在一起的动作：

    [HttpGet]
    public ActionResult Test()
    {
        return View(new SomeModel());
    }

    [HttpPost]
    public ActionResult Test([ValueProvider(typeof(MyValueProvider))]SomeModel model)
    {
        return View(model);
    }
于 2013-03-03T18:06:54.580 回答
3

想出了如何做到这一点。首先，创建一个自定义模型绑定器，它在构造函数中采用值提供者类型 - 但继承自默认模型绑定器。这允许您将标准模型绑定与自定义值提供程序一起使用：

/// <summary>
/// Uses default model binding, but sets the value provider it uses
/// </summary>
public class SetValueProviderDefaultModelBinder : DefaultModelBinder
{
    private Type _ValueProviderType;

    public SetValueProviderDefaultModelBinder(Type valueProviderType)
    {
        if (valueProviderType.GetInterface(typeof(IValueProvider).Name) == null)
            throw new ArgumentException("Type " + valueProviderType + " must implement interface IValueProvider.", "valueProviderType");

        _ValueProviderType = valueProviderType;
    }

    /// <summary>
    /// Before binding the model, set the IValueProvider it uses
    /// </summary>
    public override object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
    {
        bindingContext.ValueProvider = GetValueProvider();

        return base.BindModel(controllerContext, bindingContext);
    }

    private IValueProvider GetValueProvider()
    {
        return (IValueProvider)Activator.CreateInstance(_ValueProviderType);
    }
}

然后我们创建一个模型绑定属性，它将在上面创建的自定义模型绑定器中注入值提供者类型，并将其用作模型绑定器：

/// <summary>
/// On the default model binder, replaces the current value provider with the specified value provider.  Cannot use custom model binder with this.
[AttributeUsage(AttributeTargets.Class | AttributeTargets.Class | AttributeTargets.Enum | AttributeTargets.Interface | AttributeTargets.Parameter | AttributeTargets.Struct, AllowMultiple = false, Inherited = false)]
public class SetValueProviderAttribute : CustomModelBinderAttribute
{
    // Originally, this was an action filter, that OnActionExecuting, set the controller's IValueProvider, expecting it to be picked up by the default model binder
    // when binding the model.  Unfortunately, OnActionExecuting occurs AFTER the IValueProvider is set on the DefaultModelBinder.  The only way around this is
    // to create a custom model binder that inherits from DefaultModelBinder, and in its BindModel method set the ValueProvider and then do the standard model binding.

    public SetValueProviderAttribute(Type valueProviderType)
    {
        if (valueProviderType.GetInterface(typeof(IValueProvider).Name) == null)
            throw new ArgumentException("Type " + valueProviderType + " must implement interface IValueProvider.", "valueProviderType");

        _ValueProviderType = valueProviderType;
    }

    private Type _ValueProviderType;

    public override IModelBinder GetBinder()
    {
        var modelBinder = new SetValueProviderDefaultModelBinder(_ValueProviderType);
        return modelBinder;
    }
}
于 2011-12-28T18:18:16.850 回答