c# - How do I customize List<T>? -

this question exact duplicate of:

• error 7, argument 1: cannot convert ' ' ' ' 3 answers

i trying customize list. have figured out coming across problem. here code working with:

public class myt {     public int id { get; set; }     public myt set(string line)     {         int x = 0;          this.id = convert.toint32(line);          return this;     } }  public class mylist<t> : list<t> t : myt, new() {     internal t add(t n)     {         read();         add(n);         return n;     }     internal mylist<t> read()     {         clear();         streamreader sr = new streamreader(@"../../files/" + gettype().name + ".txt");         while (!sr.endofstream)             add(new t().set(sr.readline())); //<----here error!         sr.close();         return this;     } }  public class customer : myt {     public int id { get; set; }     public string firstname { get; set; }     public string lastname { get; set; } }  public class item : myt {     public int id { get; set; }     public string category { get; set; }     public string name { get; set; }     public double price { get; set; } }  public class myclass {     mylist<customer> customers = new mylist<customer>();     mylist<item> items = new mylist<item>(); } 

in code, can see trying create customize list. here see 2 of many classes have. of classes have id. of classes matched custom list. problem seems in mylist<t>.read() - add(new t().set(sr.readline())); lastly, myt can not converted t. need know how fix it.

the set method returns type myt instead of specific type. make generic can return specific type:

public t set<t>(string line) t : myt {     int x = 0;     this.id = convert.toint32(line);     return (t)this; } 

usage:

add(new t().set<t>(sr.readline())); 

or cast reference specific type:

add((t)(new t().set(sr.readline())));