C # Query [Study Notes] by LINQ ],

C # Query [Study Notes] by LINQ ],
[LINQ query] case: first define two classes: Master and KongFu, and then define variables in these two classes

1.  1 class Master 2 { 3     publicintId{ get;set;} 4     publicstringName{ get;set;} 5     publicintAge{ get;set;} 6     publicstringKongfu{ get;set;} 7     publicstringMenPai{ get;set;} 8     publicintLevel{ get;set;} 9     public overide string ToString()10    {11         return string.Fromat("Id:{0},Name:{1},Age:{2},Kongfu:{3},MenPai:{4},Level:{5}", Id, Name, Age, Kongfu, Menpai, Leve)12    }13 }    

    1 class KongFu 2 { 3    public int Id { get;set;} 4    public string Name { get;set;} 5    public int Power { get;set;} 6  7    public override string ToString() 8    { 9       return string.Format("Id:{0},Name:{1},Power:{2}", Id, Name, Power);10    }11 }

    

   1 static void Main (String [] args) 2 {3 var master = newList <Master> () 4 {5 newMaster () {Id = 1, Name = "Huang Rong ", age = 18, Menpai = "", Kongfu = "" ", Level = 9}, 6 newMaster () {Id = 2, Name =" ", age = 70, Menpai = "", Kongfu = "" ", Level = 10}, 7 newMaster () {Id = 3, Name =" Guo Jing ", age = 22, Menpai = "", Kongfu = "", Level = 10}, 8 newMaster () {Id = 4, Name = "", age = 50, Menpai = "Mingjiao", Kongfu = "sunflower Collection", Level = 1}, 9 newMaster () {Id = 5, Name = "Invincible ", age = 35, Menpai = "Mingjiao", Kongfu = "sunflower Collection", Level = 10}, 10 newMaster () {Id = 6, Name = "Lin pingzhi ", age = 23, Menpai = "Huashan", Kongfu = "sunflower Collection", Level = 7}, 11 newMaster () {Id = 7, Name = "Yue Bu ", age = 50, Menpai = "Huashan", Kongfu = "sunflower Collection", Level = 8}, 12 newMaster () {Id = 8, Name = "Ling huchong ", age = 23, Menpai = "Huashan", Kongfu = "Gu JIU Jian", Level = 10}, 13 newMaster () {Id = 9, Name = "Mei chaofeng ", age = 23, Menpai = "Plum Blossom Island", Kongfu = "jiuyin Zhenjing", Level = 10}, 14 newMaster () {Id = 10, Name = "Yellow pharmacist", Age = 23, menpai = "Plum Blossom Island", Kongfu = "", Level = 10}, 15 newMaster () {Id = 11, Name = "", Age = 23, menpai = "Huashan", Kongfu = "lone nine swords", Level = 10} 16}; 17 var kongfu = newList <KongFu> () 18 {19 newKongFu () {Id = 1, Name = "dongles", Power = 95}, 20 newKongFu () {Id = 2, Name = "", Power = 100 }, 21 newKongFu () {Id = 3, Name = "", Power = 100}, 22 newKongFu () {Id = 4, Name =" ", power = 100}, 23 newKongFu () {Id = 5, Name = "jiuyin Zhenjing", Power = 100}, 24 newKongFu () {Id = 6, name = "Power = 100}, 25}; 26}

Start to create a query:

[First]: Find the List with a Level greater than 8 to var result = new List <Master> (); foreach (var item in master) {if (item. level> 8) {result. add (item) ;}}foreach (var item in result) {Console. writeLine (item. toString (); // If ToString () is not specified, it exists by default.} Console. readKey (); // you need to create the ToString () method in the master class and KongFu, because after the query is complete, traverse (foreach) h will see the following error [2]: Use the professional query language to search and sort // from: indicates which set to search ...... Where: search criteria ...... Select: return result list var result2 = from m in master where m. level <10 // query condition orderby m. level // sort orderby m in ascending order based on level. level descending // sort select m in descending order by level; foreach (var item in result2) {Console. writeLine (item);} Console. readKey (); [search and sort by conditions] var ressult22 = from m in master. where (m => m. level <10 ). orderBy (m => m. age) // OrderBy & OrderByDescending select m in ascending and descending order; foreach (var item in ressult22) {Console. writeLine (item);} Console. readKey (); [3]: Call the function method to implement the search function var result3 = master. where (T1); foreach (var item in result3) {Console. writeLine (item);} Console. readKey (); // the class to be called static bool T1 (Master m) {if (m. level <10) {return true;} else {return false;} [fourth]: Use the lamada expression to find var result4 = master. where (m => m. level <10); // lamada expression parameter => Expression foreach (var item in result4) {Console. writeLine (item);} Console. readKey (); [type 5]: combine the two lists to form a Count (master) * Count (Kongfu) list of var result5 = from m in master from f in kongfu select new {mm = m, ff = f}; // foreach (var item in result5) {Console. writeLine (item);} Console. readKey ()
[Sixth]: query a master. level = Kongfu. id, when the two information var result6 = from m in master from f in kongfu // where m. level = f. id where m. kongfu = f. name & f. power> 90 select new {mm = m, ff = f}; foreach (var item in result6) {Console. writeLine (item);} Console. readKey ();
[7]: achieve the same attributes in the master and Kongfu. Output var result7 = from m in master // put the information in the kongfu list into k and select m. kongfu = k. join k in kongfu on m. kongfu equals k. name select new {mm = m, kk = k}; foreach (var item in result7) {Console. writeLine (item);} Console. readKey (); [eighth type]: one person practices one skill, one skill, how many people practice var result8 = from k in kongfu join m in master on k. name equals m. kongfu into groups // classify martial arts experts to see which kung fu is practiced by orderby groups. count () // select new {kongfu = k, count = groups according to the practitioner. count ()}; // groups. count: Get foreach (var item in result8) {Console. writeLine (item);} Console. readKey ();

// Put people with the same practices together and output the information of master and kongfu var result = from k in kongfu join m in master on k. name equals m. kongfu select new {mm = m, kk = k}; foreach (var item in result) {Console. writeLine (item);} Console. readKey ();
[Ninth]: grouping by the gang, var result9 = from m in master group m by m. menpai // group the sects and put them into m. into p // indicates putting them in p select new {count = p. count (), key = p. key}; // count = p. count () indicates the number of people in this group // key = p. key indicates the score, that is, the keyword "Key" is Menpai foreach (var item in result9) {Console. writeLine (item);} Console. readKey (); [10]: Determine whether the element in the sequence meets the condition Any. In the internal loop, traverse each element according to m => m. menpai determines whether the condition bool result10 = master is met. any (m => m. menpai = ""); Console. writeLine (result10); Console. readKey ();

From Weizhi note (Wiz)