使用Lambda表达式

Question

我用下面的实体框架代码优先pattern.I'm数据模型的新的LINQ Lambda表达式获取最低价格清单列表

问题：

我想计算单行程已在ItineraryPackagePrice

public class Region 
{ 
    public int RegionID { get; set; } 

    [Required] 
    [StringLength(100, ErrorMessage = "The {0} must be at least {2} characters long.", MinimumLength = 3)] 
    public string Name { get; set; } 

    [StringLength(100, ErrorMessage = "The {0} must be at least {2} characters long.", MinimumLength = 3)] 
    public string Type { get; set; }    

    public int? ParentID { get; set; }  

    public virtual Region Parent { get; set; } 

    public virtual ICollection<Itinerary> Itinerarys { get; set; } 

} 

public class Itinerary 
{   
    public int ItineraryID { get; set; } 

    [Required] 
    [StringLength(100, ErrorMessage = "The {0} must be at least {2} characters long.", MinimumLength = 3)] 
    public string Name { get; set; } 

    [StringLength(50, ErrorMessage = "The {0} must be at least {2} characters long.", MinimumLength = 3)] 
    public string QuoteReferenceNo { get; set; }  

    public virtual ICollection<Region> Regions { get; set; } 

    public virtual ICollection<ItineraryPackagePrice> ItineraryPackagePrices { get; set; } 
} 

public class ItineraryPackagePrice 
{ 
    public int ItineraryPackagePriceID { get; set; } 

    [DataType(DataType.Currency)] 
    [Column(TypeName = "money")] 
    public decimal Price { get; set; }   

    public int ItineraryID { get; set; } 

    public virtual Itinerary Itinerary { get; set; } 
} 

Lambda表达式最低价格值：

var db = new dbContext(); 
var siblingRegions = db.Regions.Where(s => s.ParentID == Model.Region.RegionID).OrderBy(s => s.Name); 

// iterating on each resion 
foreach (var subreg in siblingRegions) 
{ 
    var singleItinerary = subreg.Itinerarys. 
           Single(obj => 
            new { 
            Min=obj.ItineraryPackagePrices. 
            Min(k=>k.Price)}); 
    //how can I write a query here to calculate minimum price 


} 

Answer 1

试试这个： -

var siblingRegions = db.Regions.SelectMany(x => x.Itinerarys) 
           .SelectMany(x => x.ItineraryPackagePrices) 
           .OrderBy(x => x.Price).FirstOrDefault(); 

Answer 2

 var minimumPrice = decimal.MaxValue; 
     Itinerary minimumIteneray = null; 
     foreach (var subreg in regions) 
     { 
      foreach (var itinerary in subreg.Itinerarys) 
      { 
       var minimum = itinerary.ItineraryPackagePrices.Max(p => p.Price); 
       if (minimum < minimumPrice) 
       { 
        minimumPrice = minimum; 
        minimumIteneray = itinerary; 
       } 
      } 
     }