Several Methods to remove repeated items in the list set

Several methods have been tried to remove duplicate data because list is used. Recorded here...

Test data:

List < String > Li1 = New List < String > { "  8  " , "  8  " , "  9  " , "  9 " , "  0  " , "  9  "  }; List < String > Li2 = New List < String > { "  Zhang San  " , " Zhang San  " , "  Li Si  " , "  Zhang San  " , "  Wang Wu  " , "  Li Si  " }; List < String > Li3 = New List < String > { "  A  " , "  A  " , "  C  " , "  A  " , "  C  " ,"  D  "  }; List < String > LI4 = New List < String > { "  12  " , "  18  " , "  19  " , "  19  " , "  10  " , "  19  " };

Method 1:

 
Hashset <String> HS =NewHashset <String> (Li1 );//The duplicate data has been removed and saved in the hashset.
 

 

Method 2:

For(IntI =0; I <li2.count; I ++)//The number of external Loops{For(IntJ = li2.count-1; J> I; j --)//The number of times an internal loop is compared with an external loop.{If(Li2 [I] =Li2 [J]) {li2.removeat (j );}}}
 

 

Method 3:

 // Replace the same with null.              For ( Int I = 0 ; I <li3.count; I ++ ){  For ( Int J = 0 ; J <li3.count; j ++ ){  If (I = J) Continue  ;  If (Li3 [I] =Li3 [J]) {li3 [J] = "  Null  "  ;}}} 

 

Method 4:

 //  This method is the same as above, but it just changes the logic.              For ( Int I = 0 ; I <li4.count- 1 ; I ++ ){ For ( Int J = 0 ; J <li4.count; j ++ ){  If (I! = J ){  If (LI4 [I] = LI4 [J]) {LI4 [J] = "  Null  "  ;}}}} 

 

Final output

Console. writeline ( "  The value after Li1 deduplication is  "  ); HS. tolist (). foreach (item => Console. writeline (item); console. writeline (  "  The value after li2 deduplication is  "  ); Li2.foreach (item => Console. writeline (item); console. writeline (  "  The value after li3 deduplication is "  ); Li3.foreach (item => Console. writeline (item); console. writeline (  "  The value after LI4 deduplication is  "  ); Li4.foreach (item => Console. writeline (item ));

 

 

Null is not removed. Remove it when using it.

 

Of course. There are many other methods. For example, you can use either of the following functions: remove the duplicate title content in modellist, Which is case insensitive.

  Class  Program {  Static  Void Main ( String  [] ARGs) {list <Model> modellist = New List <model> (){  New Model () {id = 1 , Title = "  ABCDE  "  },  New Model () {id = 2 , Title ="  ABCDE  "  },  New Model () {id = 3 , Title = "  ABCDE  "  },  New Model () {id = 4 , Title = "  A  " },  New Model () {id = 5 , Title = "  A  "  }}; Console. Read ();}}  Public   Class  Model {  Public   Int Id { Get ; Set ;}  Public   String Title { Get ; Set  ;}} 

 

Solution 1:The premise for comparison here is the object hashCodeEqual. Otherwise, it will not be compared because the hash code is not equal. The two objects are obviously not equal.

//Define a class that inherits the iequalitycomparer InterfacePublic ClassModelcomparer: iequalitycomparer <model>{Public BoolEquals (Model X, model Y ){ReturnX. Title. toupper () =Y. Title. toupper ();}Public IntGethashcode (Model OBJ ){ReturnOBJ. Title. toupper (). gethashcode ();}}
 

Call:

Modellist = modellist. Distinct (NewModelcomparer (). tolist ();
 

 

Solution 2:

 
VaRTitle = modellist. groupby (M => M. Title. tolower (). Trim (). Select (M =>New{Id =M. firstordefault (). Id}); modellist= Modellist. Where (M => title. Select (mo =>Mo. ID). Contains (M. ID). tolist ();Foreach(VaRItemInModellist) {console. writeline (item. ID+"\ T"+Item. Title );}
 

 

Of course. If you only compare two values for equality.

List <String> Li1 =NewList <String> {"8","8","9","8","0","9"}; Li1= Li1.distinct (). tolist ();