Web API 验证不使用自定义模型绑定器触发

Question

我正在使用 Web API 5 构建 Web 服务。我正在通过扩展 IModelBinder 接口以将复杂类型作为参数映射到操作来实现自定义模型绑定器。绑定部分工作正常。但是模型验证不会发生。 ModelState.IsValid 始终为真。

public class PagingParamsVM
{
        [Range(1, Int32.MaxValue, ErrorMessage = "Page must be at least 1")]
        public int? Page { get; set; }

        [Range(1, Int32.MaxValue, ErrorMessage = "Page size must be at least 1")]
        public int? PageSize { get; set; }
}

public class PaginationModelBinder : IModelBinder
{
        public bool BindModel(HttpActionContext actionContext, ModelBindingContext bindingContext)
        {
              var model = (PagingParamsVM)bindingContext.Model ?? new PagingParamsVM();
              //model population logic
              .....

              bindingContext.Model = model;
              return true;
        }
}

public IEnumerable<NewsItemVM> Get([ModelBinder(typeof(PaginationModelBinder))]PagingParamsVM pegination)
{
            //Validate(pegination); //if I call this explicitly ModelState.IsValid is set correctly.
            var valid = ModelState.IsValid; //this is always true
}

public class ModelStateValidationActionFilter : ActionFilterAttribute
{
        public override void OnActionExecuting(HttpActionContext actionContext)
        {
            var valid = actionContext.ModelState.IsValid //this is always true.
        }
}

如果我显式调用 Validate() 或使用 [FromUri] 属性，则 ModelState.IsValid 设置正确。

public IEnumerable<NewsItemVM> Get([FromUri]PagingParamsVM pegination)
{
            var valid = ModelState.IsValid;
}

我应该在模型绑定器中实现验证部分吗？如果是这样我应该如何实施？

Answer 1

DefaultModelBinder.CreateModel 应该可以帮助您保持模型状态：

public class PaginationModelBinder : DefaultModelBinder
{
    protected override object CreateModel(ControllerContext controllerContext, ModelBindingContext bindingContext, Type modelType)
    {
        if(modelType == typeof(PagingParamsVM))
        {
            var page = default(int?);
            var model = bindingContext.Model;
            var valueProvider = bindingContext.ValueProvider;
            var pageValue = valueProvider.GetValue("Page");
            var tmp = default(int);
            if(pageValue != null && int.TryParse(pageValue.AttemptedValue, out tmp))
            {
                page = tmp;
            }

            var pageSize = default(int?);
            var sizeValue = valueProvider.GetValue("PageSize");
            if(sizeValue != null && int.TryParse(sizeValue.AttemptedValue, out tmp))
            {
                pageSize = tmp;
            }
            return new PagingParamsVM { Page = page, PageSize = pageSize };
        }
        return base.CreateModel(controllerContext, bindingContext, modelType);
    }
}

使用 binder 的 web api 控制器可以是：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Http;
using System.Web.Mvc;

public class NewsItemController : ApiController
{
    public IEnumerable<NewsItemVM> Get([ModelBinder(typeof(PaginationModelBinder))]PagingParamsVM pegination)
    {
        //Validate(pegination); //if I call this explicitly ModelState.IsValid is set correctly.
        var valid = ModelState.IsValid; //this is always true
        return Enumerable.Empty<NewsItemVM>();
    }
}

Answer 2

我找到了答案。可以在自定义模型绑定器中调用默认验证过程，如下所示，

public abstract class PaginationModelBinder : IModelBinder
{
        public bool BindModel(HttpActionContext actionContext, ModelBindingContext bindingContext)
        {
              var model = (PagingParamsVM)bindingContext.Model ?? new PagingParamsVM();
              //model population logic
              .....

              bindingContext.Model = model;

              //following lines invoke default validation on model
              bindingContext.ValidationNode.ValidateAllProperties = true;
              bindingContext.ValidationNode.Validate(actionContext);

              return true;
        }
}

感谢大家的支持。