合併自定義對象的多個列表的內容 - C＃

Question

我有一類項目作爲

public class Project 
{ public int ProjectId { get; set; } 
    public string ProjectName { get; set; } 
    public string Customer { get; set; } 
    public string Address{ get; set; } 
} 

，我有3所列出

List<Project> lst1; List<Project> lst2; List<Project> lst3; 

lst1包含Person對象與專案編號和項目名。

ProjectId =1, ProjectName = "X", Customer = null, Address = null

ProjectId =2, ProjectName = "Y", Customer = null, Address = null

lst2包含Person對象與專案編號和客戶

ProjectId =1,ProjectName = null, Customer = "c1", Address = null

ProjectId =2,ProjectName = null, Customer = "c2", Address = null 和

lst3包含Person對象與專案編號和地址

ProjectId = 2, ProjectName = null, Customer =null, Address = "a2"。

考慮到有多個這樣的記錄在每個列表和專案是潮頭對於每一個項目，我怎麼能合併/組合這些列表以獲得一個列表與合併對象

ProjectId=1, ProjectName="X", Customer="c1", address="a1"

ProjectId=2, ProjectName="Y", Customer="c2", address="a2"

我發現這些鏈接類似，並試圖用它，但不能滿足結果

Create a list from two object lists with linq

How to merge two lists using LINQ?

謝謝。

Answer 1

這可以通過多步驟方法完成。首先，定義一個Func<Project, Project, Project>來處理實際的記錄合併。也就是說，您正在定義一個簽名相當於public Project SomeMethod(Project p1, Project p2)的方法。該方法實現了上面概述的合併邏輯。

Func<Project, Project, Project> mergeFunc = (p1,p2) => new Project 
    { 
     ProjectId = p1.ProjectId, 
     ProjectName = p1.ProjectName == null ? p2.ProjectName : p1.ProjectName, 
     Customer = p1.Customer == null ? p2.Customer : p1.Customer, 
     Address = p1.Address == null ? p2.Address : p1.Address  
    }; 

var output = lst1.Concat(lst2).Concat(lst3) 
       .GroupBy(x => x.ProjectId, (k, g) => g.Aggregate(mergeFunc)); 

這裏有一個快速和骯髒的測試：接下來，我們通過ProjectId將它們分組，用我們的合併代表如在GroupBy過載的聚合函數，它接受一個結果選擇前級連在一起的列表的元素與輸出一起上述邏輯：

List<Project> lst1; List<Project> lst2; List<Project> lst3; 
lst1 = new List<Project> 
    { 
     new Project { ProjectId = 1, ProjectName = "P1" }, 
     new Project { ProjectId = 2, ProjectName = "P2" }, 
     new Project { ProjectId = 3, ProjectName = "P3" } 
    }; 
lst2 = new List<Project> 
    { 
     new Project { ProjectId = 1, Customer = "Cust1"}, 
     new Project { ProjectId = 2, Customer = "Cust2"}, 
     new Project { ProjectId = 3, Customer = "Cust3"} 
    }; 
lst3 = new List<Project> 
    { 
     new Project { ProjectId = 1, Address = "Add1"}, 
     new Project { ProjectId = 2, Address = "Add2"}, 
     new Project { ProjectId = 3, Address = "Add3"} 
    }; 

Func<Project, Project, Project> mergeFunc = (p1,p2) => new Project 
    { 
     ProjectId = p1.ProjectId, 
     ProjectName = p1.ProjectName == null ? p2.ProjectName : p1.ProjectName, 
     Customer = p1.Customer == null ? p2.Customer : p1.Customer, 
     Address = p1.Address == null ? p2.Address : p1.Address  
    }; 

var output = lst1 
    .Concat(lst2) 
    .Concat(lst3) 
    .GroupBy(x => x.ProjectId, (k, g) => g.Aggregate(mergeFunc)); 

IEnumerable<bool> assertedCollection = output.Select((x, i) => 
    x.ProjectId == (i + 1) 
    && x.ProjectName == "P" + (i+1) 
    && x.Customer == "Cust" + (i+1) 
    && x.Address == "Add" + (i+1)); 

Debug.Assert(output.Count() == 3); 
Debug.Assert(assertedCollection.All(x => x == true)); 

--- ---輸出

IEnumerable<Project> (3 items) 
ProjectId ProjectName Customer Address 
1 P1 Cust1 Add1 
2 P2 Cust2 Add2 
3 P3 Cust3 Add3 

Answer 2

我假設列表包含相同數量的項目並按ProjectId排序。

List<Project> lst1; List<Project> lst2; List<Project> lst3 

如果列表沒有排序，您可以先排序。

list1.Sort(p => p.ProjectId); 
list2.Sort(p => p.ProjectId); 
list3.Sort(p => p.ProjectId); 

對於合併對象

List<Project> list4 = new List<Project>(); 
for(int i=1; i<list.Count; i++) 
{ 
    list4.Add(new Project 
    { 
     ProjectId = list1[i].ProjectId; 
     ProjectName = list1[i].ProjectName; 
     Customer = list2[i].Customer; 
     Address = list3[i].Address; 
    }); 

} 

Answer 3

我相信在folloing是如何LINQ Join作品：

var mergedProjects = 
    lst1 
     .Join(lst2, 
      proj1 => proj1.ProjectID, 
      proj2 => proj2.ProjectID, 
      (proj1, proj2) => new { Proj1 = proj1, Proj2 = proj2 }) 
     .Join(lst3, 
      pair => pair.Proj1.ProjectID, 
      proj3 => proj3.ProjectID, 
      (pair, proj3) => new Project 
      { 
       ProjectID = proj3.ProjectID, 
       ProjectName = pair.Proj1.ProjectName, 
       Customer = pair.Proj2.Customer, 
       Address = proj3.Address 
      }); 

這將不會返回在ProjectID不所有找到的任何結果三個名單。

如果這是一個問題，我認爲你最好是手動完成而不是使用LINQ。

Answer 4

雖然矯枉過正，我很想讓這個擴展方法：

public static List<T> MergeWith<T,TKey>(this List<T> list, List<T> other, Func<T,TKey> keySelector, Func<T,T,T> merge) 
{ 
    var newList = new List<T>(); 
    foreach(var item in list) 
    { 
     var otherItem = other.SingleOrDefault((i) => keySelector(i).Equals(keySelector(item))); 
     if(otherItem != null) 
     { 
      newList.Add(merge(item,otherItem)); 
     } 
    } 
    return newList; 
} 

然後用法是：

var merged = list1 
    .MergeWith(list2, i => i.ProjectId, 
     (lhs,rhs) => new Project{ProjectId=lhs.ProjectId,ProjectName=lhs.ProjectName, Customer=rhs.Customer}) 
    .MergeWith(list3,i => i.ProjectId, 
     (lhs,rhs) => new Project{ProjectId=lhs.ProjectId,ProjectName=lhs.ProjectName, Customer=lhs.Customer,Address=rhs.Address}); 

活生生的例子：http://rextester.com/ETIVB14254

Answer 5

使用查找，你可以做它是這樣的：

 List<Project> lst = lst1.Union(lst2).Union(lst3).ToLookup(x => x.ProjectId).Select(x => new Project() 
     { 
      ProjectId = x.Key, 
      ProjectName = x.Select(y => y.ProjectName).Aggregate((z1,z2) => z1 ?? z2), 
      Customer = x.Select(y => y.Customer).Aggregate((z1, z2) => z1 ?? z2), 
      Address = x.Select(y => y.Address).Aggregate((z1, z2) => z1 ?? z2) 
     }).ToList(); 

Answer 6

這假設您想要取第一個非空值，或恢復爲默認值 - 在此情況下，字符串爲null。

private static IEnumerable<Project> GetMergedProjects(IEnumerable<List<Project>> projects) 
{ 
    var projectGrouping = projects.SelectMany(p => p).GroupBy(p => p.ProjectId); 
    foreach (var projectGroup in projectGrouping) 
    { 
     yield return new Project 
          { 
           ProjectId = projectGroup.Key, 
           ProjectName = 
            projectGroup.Select(p => p.ProjectName).FirstOrDefault(
             p => !string.IsNullOrEmpty(p)), 
           Customer = 
            projectGroup.Select(c => c.Customer).FirstOrDefault(
             c => !string.IsNullOrEmpty(c)), 
           Address = 
            projectGroup.Select(a => a.Address).FirstOrDefault(
             a => !string.IsNullOrEmpty(a)), 
          }; 
    } 
} 

如果需要，您也可以將其作爲擴展方法。