使用ASP.NET Web API。是否有一种方法可以在参数为空时自动返回状态码400？我发现了这个问题，但那是一个应用于所有方法的全局解决方案，我想按每个方法每个参数来做。
所以，例如，这就是我目前正在做的：
public HttpResponseMessage SomeMethod(SomeNullableParameter parameter)
{
if (parameter == null)
throw new HttpResponseException(HttpStatusCode.BadRequest);
// Otherwise do more stuff.
}
我真的很想做这样的事情（请注意所需的属性）：
public HttpResponseMessage SomeMethod([Required] SomeNullableParameter parameter)
{
// Do stuff.
}
我的解决方案是创建一个自定义过滤器并将其注册为全局过滤器。该过滤器将检查所有请求参数是否包含RequiredAttribute。如果找到这个属性，则检查请求中是否传递了该参数（非空），如果为null，则返回状态码400。我还向过滤器添加了缓存，以存储每个请求所需的参数，以避免反射对未来调用的影响。令人惊喜的是，它也适用于值类型，因为ActionContext将参数存储为对象。
编辑 - 根据tecfield的评论更新解决方案
public class RequiredParametersFilter : ActionFilterAttribute
{
// Cache used to store the required parameters for each request based on the
// request's http method and local path.
private readonly ConcurrentDictionary<Tuple<HttpMethod, string>, List<string>> _Cache =
new ConcurrentDictionary<Tuple<HttpMethod, string>, List<string>>();
public override void OnActionExecuting(HttpActionContext actionContext)
{
// Get the request's required parameters.
List<string> requiredParameters = this.GetRequiredParameters(actionContext);
// If the required parameters are valid then continue with the request.
// Otherwise, return status code 400.
if(this.ValidateParameters(actionContext, requiredParameters))
{
base.OnActionExecuting(actionContext);
}
else
{
throw new HttpResponseException(HttpStatusCode.BadRequest);
}
}
private bool ValidateParameters(HttpActionContext actionContext, List<string> requiredParameters)
{
// If the list of required parameters is null or containst no parameters
// then there is nothing to validate.
// Return true.
if (requiredParameters == null || requiredParameters.Count == 0)
{
return true;
}
// Attempt to find at least one required parameter that is null.
bool hasNullParameter =
actionContext
.ActionArguments
.Any(a => requiredParameters.Contains(a.Key) && a.Value == null);
// If a null required paramter was found then return false.
// Otherwise, return true.
return !hasNullParameter;
}
private List<string> GetRequiredParameters(HttpActionContext actionContext)
{
// Instantiate a list of strings to store the required parameters.
List<string> result = null;
// Instantiate a tuple using the request's http method and the local path.
// This will be used to add/lookup the required parameters in the cache.
Tuple<HttpMethod, string> request =
new Tuple<HttpMethod, string>(
actionContext.Request.Method,
actionContext.Request.RequestUri.LocalPath);
// Attempt to find the required parameters in the cache.
if (!this._Cache.TryGetValue(request, out result))
{
// If the required parameters were not found in the cache then get all
// parameters decorated with the 'RequiredAttribute' from the action context.
result =
actionContext
.ActionDescriptor
.GetParameters()
.Where(p => p.GetCustomAttributes<RequiredAttribute>().Any())
.Select(p => p.ParameterName)
.ToList();
// Add the required parameters to the cache.
this._Cache.TryAdd(request, result);
}
// Return the required parameters.
return result;
}
}
ConcurrentDictionary 而不是不安全的普通 Dictionary！ - tecfieldPOST模型有效吗？即参数是某种类，该类具有被标记为[Required]的字段。 - Zero3[Required] 属性，然后检查 ModelState 是否为 IsValid。我们可以使用来自 Microsoft.AspNetCore.Mvc.ModelBinding 命名空间的 BindRequired。
public async Task<ActionResult<IEnumerable<Numbers>>> GetAll([BindRequired, FromQuery]string[] numbers)
{
var result = await _service.GetAllDetails(numbers);
return Ok(result);
}
然后你的Swagger看起来会像下面这样。
[AttributeUsage(AttributeTargets.Method)]
public sealed class CheckRequiredModelAttribute : ActionFilterAttribute
{
public override void OnActionExecuting(ActionExecutingContext context)
{
var requiredParameters = context.ActionDescriptor.Parameters.Where(
p => ((ControllerParameterDescriptor)p).ParameterInfo.GetCustomAttribute<RequiredModelAttribute>() != null).Select(p => p.Name);
foreach (var argument in context.ActionArguments.Where(a => requiredParameters.Contains(a.Key, StringComparer.Ordinal)))
{
if (argument.Value == null)
{
context.ModelState.AddModelError(argument.Key, $"The argument '{argument.Key}' cannot be null.");
}
}
if (!context.ModelState.IsValid)
{
var errors = context.ModelState.Values.SelectMany(v => v.Errors).Select(e => e.ErrorMessage);
context.Result = new BadRequestObjectResult(errors);
return;
}
base.OnActionExecuting(context);
}
}
[AttributeUsage(AttributeTargets.Parameter)]
public sealed class RequiredModelAttribute : Attribute
{
}
services.AddMvc(options =>
{
options.Filters.Add(typeof(CheckRequiredModelAttribute));
});
public async Task<IActionResult> CreateAsync([FromBody][RequiredModel]RequestModel request, CancellationToken cancellationToken)
{
//...
}
被接受的解决方案会自行报告任何错误。对于MVC5来说，更合适的方法是让控制器处理（通过模型验证）任何错误的报告，就像这样：
using System.ComponentModel.DataAnnotations;
using System.Linq;
using System.Web.Http.Controllers;
using System.Web.Http.Filters;
using System.Web.Http.ModelBinding;
[AttributeUsage(AttributeTargets.Class | AttributeTargets.Method, AllowMultiple = true)]
public sealed class ValidateParametersAttribute : ActionFilterAttribute
{
public override void OnActionExecuting(HttpActionContext context)
{
var descriptor = context.ActionDescriptor;
if (descriptor != null)
{
var modelState = context.ModelState;
foreach (var parameterDescriptor in descriptor.GetParameters())
{
EvaluateValidationAttributes(
suppliedValue: context.ActionArguments[parameterDescriptor.ParameterName],
modelState: modelState,
parameterDescriptor: parameterDescriptor
);
}
}
base.OnActionExecuting(context);
}
static private void EvaluateValidationAttributes(HttpParameterDescriptor parameterDescriptor, object suppliedValue, ModelStateDictionary modelState)
{
var parameterName = parameterDescriptor.ParameterName;
parameterDescriptor
.GetCustomAttributes<object>()
.OfType<ValidationAttribute>()
.Where(x => !x.IsValid(suppliedValue))
.ForEach(x => modelState.AddModelError(parameterName, x.FormatErrorMessage(parameterName)));
}
}
然后，您可以通过WebApiConfig.cs在全局范围内插入它：
config.Filters.Add(new ValidateParametersAttribute());