来自不同类的 Lambda 表达式中的多个 Where 子句

Posted 2023-04-01

【中文标题】来自不同类的 Lambda 表达式中的多个 Where 子句

【英文标题】：Multiple Where clauses in Lambda expressions from different classes

【发布时间】：2021-09-04 05:18:08

【问题描述】：

我创建了一个名为AppRequest的主类，在它之下，还有其他类Suspense、SuspenseDetails。 当我查询数据时，我想从 AppRequest 查询一个，从 Suspense 查询一个，从 SuspenseDetails 查询一个。

代码是这样写的

int y = int.Parse(((System.Security.Claims.ClaimsIdentity)User.Identity).FindFirst("UserId").Value);
List<AppRequest> SuspencesforSettle = db.AppRequest.Where(s => s.Create_By == y).Where(s=> s.Status==true).ToList();

我想从 AppRequest 中查询 - CreatedBy 和 Status 并且还需要从 SuspenseDetails 中检查 Settle_Status。 但是，从 where 条件我只能获取 AppRequest 类下的字段。你们能帮我解决这个问题吗？

这就是我的模型设计的方式。

 public class AppRequest
    
        [Key]
        public int Id  get; set; 

        [Required]
        [Display(Name = "Request Type")]
        public int ReqType  get; set; 

        [Required]
        [Display(Name = "Requesting By")]
        public int Req_By  get; set; 

        [Required]
        [Display(Name = "Requesting Date")]
        public DateTime Req_Date  get; set;  = DateTime.Now;

        [Required]
        [Display(Name = "Request Location")]
        public int Req_Location  get; set; 

        [Required]
        [Display(Name = "Request Heading")]
        public string Req_Heading  get; set; 

        [Display(Name = "Cover Note")]
        public string Req_CoverNote  get; set; 

        [Required]
        [Display(Name = "Company Name")]
        public int Company_Id  get; set; 
        public bool Status  get; set; 
        public int Create_By  get; set; 
        public DateTime Created_Date  get; set; 
        public int Modified_By  get; set; 
        public DateTime Modified_Date  get; set;  = DateTime.Now;
        public int Approval_Status  get; set; 

        public virtual IList<Suspense> Suspense  get; set; 
     

 public class Suspense
    
        [Key]
        public int Id  get; set; 

        [Required]
        [ForeignKey("AppRequest")]
        public int Req_Id  get; set; 
        public virtual AppRequest AppRequest  get; set; 

        public virtual IList<SuspenseDetails> SuspenseDetails  get; set; 
    

 public class SuspenseDetails
    
        [Key]
        public int Id  get; set; 

        [Required]
        [ForeignKey("Suspense")]
        public int Sus_Id  get; set; 
        public virtual Suspense Suspense  get; set; 

        [Required]
        [Display(Name = "Requesting Amount")]
        public decimal Req_Amount  get; set; 

        [Required]
        [Display(Name = "Amount In Words")]
        public string Req_Amount_In_Words  get; set; 

        [Required]
        [Display(Name = "Purpose")]
        public string Purpose  get; set; 

        [Required]
        [Display(Name = "Cash Requesting for ")]
        public int Req_For  get; set; 

        public string Approved_Suspense_Id  get; set; 
        public bool Cash_Issued  get; set; 
        public int Cash_IssuedBy  get; set; 
        public DateTime? Cash_Issued_Date  get; set; 
        public bool Settled  get; set; 

    

【参考方案1】：

你可以这样写：

var result =
    db
        .AppRequest
        .Where(appRequest => appRequest.Create_By == creator)
        .Where(
            appRequest =>
            appRequest
                .Suspense
                .SelectMany(suspense => suspense.SuspenseDetails)
                .Any(suspenseDetails => suspenseDetails.Settled)
        )
        .ToList();