Cycle judgment, remove the duplicate data in the list on another list,

CodePudding user response:

Want to see the list type is an object or a single data type

A single data types directly compare whether repeated

Object, the need to write another compare

CodePudding user response:

 

Public static class ObjectExtensions 
{
Public static IEnumerable DistinctBy (this IEnumerable The source, Func KeySelector) 
{
HashSet SeenKeys=new HashSet (a); 
Foreach (TSource element in the source) 
{
If (seenKeys. Add (keySelector (element))) 
{
Yield return element; 
} 
} 
} 
} 


///& lt; Summary> 
///return subject data 
///& lt;/summary> 
[Serializable] 
Public class QuestionResult 
{
///& lt; Summary> 
///no. 
///& lt;/summary> 
Public long Id {get; set; } 

///& lt; Summary> 
///the topic content 
///& lt;/summary> 
Public string Title {get; set; } 

} 

List. DistinctBy (e=& gt; New} {e.I d) ToList (); 

CodePudding user response:

Write this do not extend his sweet

CodePudding user response:

 List List=new List () {1, 2, 3, 12, 2, 3}; 
List NewList=new List (a); 

//to heavy 
//var NewList=List. The Distinct (); 

//loop to heavy 
The foreach (var item in the List) 
{
if (! NewList. The Contains (item)) 
{
NewList. Add (item); 
} 
} 

CodePudding user response:

For a list. Select (p=& gt; P.n ame). Distinct (.) ToList ();//remove the name repeated list data

CodePudding user response:

This is a basic problem, need to first understand what is repetitive data, the processing of a reference type and value type is not the same, a reference type as long as the same value that is repeated, reference type must be the same object reference is repeated, see==and Equals the relation and distinction between, get this understood, the other is right,

CodePudding user response:

Change the version of the dictionary:

 
Var list=new List () {1, 1, 2, 2, 2, 5, 8, 5, 5, 8, 5, 5, 48, 85, 5, 54, 85}; 
Dictionary Dic=new Dictionary (a); 
Foreach (var I in the list) 
{
Dic [I]=I; 
} 
Var newList=dic. Keys; 
Foreach (var I in newList) 
{
Console. WriteLine (I); 
} 

CodePudding user response:

refer to 7th floor ziqi0716 response:

change the version of the dictionary:

 
Var list=new List () {1, 1, 2, 2, 2, 5, 8, 5, 5, 8, 5, 5, 48, 85, 5, 54, 85}; 
Dictionary Dic=new Dictionary (a); 
Foreach (var I in the list) 
{
Dic [I]=I; 
} 
Var newList=dic. Keys; 
Foreach (var I in newList) 
{
Console. WriteLine (I); 
} 

The seventh line can be output into List : var newList=dic. Keys. ToList ();

CodePudding user response:

Thank you, I want to ask is this list_ List Type judgment contained can determine whether include UserKey
If List How do I know if does it include UserKey?