Web Api必需參數

Question

使用ASP.NET Web API。如果參數爲空，有沒有辦法自動返回狀態碼400？我發現這個question，但這是一個適用於所有方法的全局解決方案，我希望按每個參數的每個方法執行此操作。

因此，舉例來說，這是我目前在做什麼：

public HttpResponseMessage SomeMethod(SomeNullableParameter parameter) 
{ 
    if (parameter == null) 
     throw new HttpResponseException(HttpStatusCode.BadRequest); 

    // Otherwise do more stuff. 
} 

我真的只是想這樣做（注意所需的屬性）：

public HttpResponseMessage SomeMethod([Required] SomeNullableParameter parameter) 
{ 
    // Do stuff. 
} 

Answer 1

最後我用是創造我全局註冊自定義過濾器的方法。過濾器檢查'RequiredAttribute'的所有請求參數。如果找到屬性，那麼它會檢查參數是否與請求一起傳遞（非空），如果爲空，則返回狀態碼400。我還爲過濾器添加了一個緩存，以便爲每個請求存儲所需的參數，以避免將來調用反射命中。我驚喜地發現，這也適用於值類型，因爲動作上下文將參數存儲爲對象。

編輯 - 更新的解決方案基於tecfield的評論

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; 
    } 

} 

Answer 2

集[必需的]，然後檢查ModelState以查看它是否爲IsValid。

這將允許所有需要的屬性在同一時間進行測試。

請參閱「在張貼」部分@Model validation in WebAPI

Answer 3

一種asp.net核心解決方案...

[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) 
{ 
    //... 
} 

Answer 4

接受的解決方案需要獨自去報到的任何錯誤。對於MVC5更合適的方法是，讓控制器手柄（通過模型驗證）的任何錯誤的報告，又名是這樣的：

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))); 
    } 
} 

然後，您可以通過WebApiConfig.cs插上普遍：

config.Filters.Add(new ValidateParametersAttribute());