DOTNET CORE WEB API 統一模型驗證攔截器

參考:

• https://code-maze.com/action-filters-aspnetcore/
• https://github.com/aspnet/AspNetCore.Docs/issues/12157
• https://docs.microsoft.com/en-us/aspnet/core/web-api/?view=aspnetcore-3.0#automatic-http-400-responses

1. 關閉默認模型驗證過濾器
   [ApiController] 默認自帶有400模型驗證，且優先級比較高，如果需要自定義模型驗證，則需要先關閉默認的模型驗證
   在StartUp.cs 中的MVC服務配置修改

   #region MVC
   services.AddMvc(o =>
   {
   }).SetCompatibilityVersion(CompatibilityVersion.Version_2_2)
   .ConfigureApiBehaviorOptions(o =>
   {
       o.SuppressModelStateInvalidFilter = true;
   });
    #endregion
   

2. 首先定義統一輸出的格式為

   {
       code:
       errors:[
           filed:
           message:
       ]
   }
   

3. 添加自定義模型驗證DTO

    public class ErrorResultDTO
       {
           /// <summary>
           /// 參數領域
           /// </summary>
           public string Field { get; set; }
   
           /// <summary>
           /// 錯誤信息
           /// </summary>
           public string Message { get; set; }   
       }
   

4.  添加過濾器
    過濾器繼承自:ActionFilterAttribute, IActionFilter
    ``` c#
    public class ModelActionFiter :ActionFilterAttribute, IActionFilter
        {
            public ModelActionFiter()
            {
            }
            public override void OnActionExecuted(ActionExecutedContext context)
            {
                
            }

           public override void OnActionExecuting(ActionExecutingContext context)
            {
                if (!context.ModelState.IsValid)
                {     
                    List<ErrorResultDTO> errorResults = new List<ErrorResultDTO>();
                    foreach (var item in context.ModelState)
                    {
                        var result = new ErrorResultDTO
                        {
                            Field = item.Key,
                            Msg = "",
                        };
                        foreach (var error in item.Value.Errors)
                        {
                            if (!string.IsNullOrEmpty(result.Msg))
                            {
                                result.Msg += '|';
                            }
                            result.Msg += error.ErrorMessage;
                        }
                        errorResults.Add(result);
                    }
                    context.Result = new BadRequestObjectResult(new
                    {
                        Code = StatusCodes.Status400BadRequest,
                       Errors = errorResults
                    });  
                }
            }
        }
    ```
5. 將寫的過濾器注冊到全局

    ``` c#  
      services.AddMvc(o =>
            {
                o.Filters.Add(new ModelActionFiter());
       })

6. 結果測試
   

7. 擴展

   • 利用攔截器來測試action 的運行時間，記錄日志，並設置時間限制，超過某個時間段自動發送郵件通知維護人員