Create a data table by querying through LINQ

Using system; <br/> using system. collections. generic; <br/> using system. LINQ; <br/> using system. text; <br/> using system. data; </P> <p> namespace usecopytotable <br/> {<br/> class Program <br/>{< br/> static void main (string [] ARGs) <br/>{< br/> usecopytodtsimple (); <br/> usesetfield (); <br/>}</P> <p> static dataset builddataset () <br/>{< br/> // create a students dataset <br/> dataset DS = new dataset ("Students"); <br/> // create a students data table, and add it to the dataset <br/> // students data table contains student information <br/> datatable dtstu = new datatable ("Students"); <br/> DS. tables. add (dtstu); <br/> // Add the column information of the student information record <br/> dtstu. columns. addrange (New datacolumn [] {<br/> New datacolumn ("name", type. getType ("system. string "), <br/> New datacolumn (" xingbie ", type. getType ("system. string "), <br/> New datacolumn (" Age ", type. getType ("system. int32 "), <br/> New datacolumn (" scoreid ", type. getType ("system. int32 "), <br/>}); <br/> // Add the row information of the Student Information <br/> dtstu. rows. add ("Zhang San", "male", 20, 1); <br/> dtstu. rows. add ("Li Si", "male", 19, 2); <br/> dtstu. rows. add ("Wang Xia", "female", 21, 3); <br/> dtstu. rows. add ("Zhao Min", "female", 22, 4); <br/> dtstu. rows. add ("Wu an", "male", 18, 5); <br/> // create a scores data table, and add it to the dataset <br/> // The scores data table contains the Student Score record <br/> datatable dtscore = new datatable ("scores"); <br/> DS. tables. add (dtscore); <br/> // Add the column information of the score record <br/> dtscore. columns. addrange (New datacolumn [] {<br/> New datacolumn ("scoreid", type. getType ("system. int32 "), <br/> New datacolumn (" math ", type. getType ("system. int32 "), <br/> New datacolumn (" Chinese ", type. getType ("system. int32 "), <br/> New datacolumn (" English ", type. getType ("system. int32 "), <br/>}); <br/> // Add a student score record <br/> dtscore. rows. add (1, 80, 75, 78); <br/> dtscore. rows. add (3, 88, 80, 60); <br/> dtscore. rows. add (4, 75, 90, 80); <br/> dtscore. rows. add (5, 59, 80, 75); <br/> // return the dataset <br/> return Ds; <br/>}</P> <p> static void usecopytodtsimple () <br/>{< br/> // obtain the dataset and the data table to be queried <br/> dataset DS = builddataset (); <br/> datatable dtstu = Ds. tables ["Students"]; <br/> datatable dtscore = Ds. tables ["scores"]; <br/> // query the students whose score is greater than 20 in query1 <br/> var query1 = <br/> from Stu in dtstu. asenumerable () <br/> from score in dtscore. asenumerable () <br/> where stu. field <int> ("scoreid") = score. field <int> ("scoreid") <br/> where (INT) STU ["Age"]> 20 <br/> select Stu; <br/> // create a new copy using the copytodatatable () method <br/> datatable newdt = query1.copytodatatable <datarow> (); <br/> // print the copy information <br/> system. console. writeline ("student list:"); <br/> foreach (VAR item in newdt. asenumerable () <br/>{< br/> system. console. writeline ("Name: {0}, Gender: {1}, age: {2}", <br/> item ["name"], item ["xingbie"], item ["Age"]); <br/>}</P> <p> static void usesetfield () <br/>{< br/> // obtain the dataset and the data table to be queried <br/> dataset DS = builddataset (); <br/> datatable dtstu = Ds. tables ["Students"]; <br/> // increase the age of all students by 2 <br/> foreach (VAR row in dtstu. asenumerable () <br/>{< br/> int age = row. field <int> ("Age"); <br/> row. setfield <int> ("Age", age + 2); <br/>}< br/> // print new student information <br/> system. console. writeline ("student list:"); <br/> foreach (VAR item in dtstu. asenumerable () <br/>{< br/> system. console. writeline ("Name: {0}, Gender: {1}, age: {2}", <br/> item ["name"], item ["xingbie"], item ["Age"]); <br/>}< br/>