c# - 属性路由值到模型/FromBody 参数

Question

在 Web API (2) 中使用属性路由时，我希望能够自动将路由参数从 URL 获取到模型参数中。这样做的原因是我的验证是在它到达操作之前在过滤器中执行的，如果没有它，附加信息就不容易获得。

考虑以下简化示例:

public class UpdateProductModel
{
    public int ProductId { get; set; }
    public string Name { get; set; }
}

public class ProductsController : ApiController 
{
    [HttpPost, Route("/api/Products/{productId:int}")]
    public void UpdateProduct(int productId, UpdateProductModel model) 
    {
         // model.ProductId should == productId, but is default (0)
    }
}

发布到此的示例代码:

$.ajax({
    url: '/api/Products/5',
    type: 'POST',
    data: {
        name: 'New Name'   // NB: No ProductId in data
    }
});

我希望模型中的 ProductId 字段在进入操作方法之前从路由参数中填充(即它对我的验证器可用)。

我不确定我需要尝试覆盖模型绑定(bind)过程的哪一部分 - 我认为这是处理 [FromBody] 部分(这是模型参数这个例子)。

在操作本身中设置它是 Not Acceptable (例如 model.ProductId = productId)，因为我需要在它到达操作之前设置它。

Answer 1

引用这篇文章Parameter Binding in ASP.NET Web API

模型绑定(bind)器

A more flexible option than a type converter is to create a custom model binder. With a model binder, you have access to things like the HTTP request, the action description, and the raw values from the route data.

To create a model binder, implement the IModelBinder interface

这是一个用于 UpdateProductModel 对象的模型绑定(bind)器，它将尝试提取路由值并使用找到的任何匹配属性来组合模型。

public class UpdateProductModelBinder : IModelBinder {

    public bool BindModel(System.Web.Http.Controllers.HttpActionContext actionContext, ModelBindingContext bindingContext) {
        if (!typeof(UpdateProductModel).IsAssignableFrom(bindingContext.ModelType)) {
            return false;
        }

        //get the content of the body and convert it to model
        object model = null;

        if (actionContext.Request.Content != null)
            model = actionContext.Request.Content.ReadAsAsync(bindingContext.ModelType).Result;

        model = model ?? bindingContext.Model
            ?? Activator.CreateInstance(bindingContext.ModelType);

        // check values provided in the route or query string 
        // for matching properties and set them on the model. 
        // NOTE: this will override any existing value that was already set.
        foreach (var property in bindingContext.PropertyMetadata) {
            var valueProvider = bindingContext.ValueProvider.GetValue(property.Key);
            if (valueProvider != null) {
                var value = valueProvider.ConvertTo(property.Value.ModelType);
                var pInfo = bindingContext.ModelType.GetProperty(property.Key);
                pInfo.SetValue(model, value, new object[] { });
            }
        }

        bindingContext.Model = model;

        return true;
    }
}

设置模型绑定(bind)器

There are several ways to set a model binder. First, you can add a [ModelBinder] attribute to the parameter.

public HttpResponseMessage UpdateProduct(int productId, [ModelBinder(typeof(UpdateProductModelBinder))] UpdateProductModel model)

You can also add a [ModelBinder] attribute to the type. Web API will use the specified model binder for all parameters of that type.

[ModelBinder(typeof(UpdateProductModelBinder))]
public class UpdateProductModel {
    public int ProductId { get; set; }
    public string Name { get; set; }
}

给定以下使用上述模型和 ModelBinder 的简化示例

public class ProductsController : ApiController {
    [HttpPost, Route("api/Products/{productId:int}")]
    public IHttpActionResult UpdateProduct(int productId, UpdateProductModel model) {
        if (model == null) return NotFound();
        if (model.ProductId != productId) return NotFound();

        return Ok();
    }
}

以下集成测试用于确认所需的功能

[TestClass]
public class AttributeRoutingValuesTests {
    [TestMethod]
    public async Task Attribute_Routing_Values_In_Url_Should_Bind_Parameter_FromBody() {
        var config = new HttpConfiguration();
        config.MapHttpAttributeRoutes();

        using (var server = new HttpTestServer(config)) {

            var client = server.CreateClient();

            string url = "http://localhost/api/Products/5";
            var data = new UpdateProductModel {
                Name = "New Name" // NB: No ProductId in data
            };
            using (var response = await client.PostAsJsonAsync(url, data)) {
                Assert.AreEqual(HttpStatusCode.OK, response.StatusCode);
            }
        }
    }
}