c# - Using yield in a while loop to return one or many objects -

i have 2 database methods. 1 fetches 1 row based on name , creates object out of it. other identical, fetches rows , creates n objects out of it. hoping use yield return share method process sqllite data, issue have in createfoofromsqlselect telling me the body of createfoofromsqlselect cannot iterator block becausefoois not iterator type. wasn't expecting that.

public foo getfoo(string name){    string sql = "select age people name = " + name;    return createfoofromselect(sql); }  public list<foo> getfoos(){    list<foo> foos = new list<foo>();    string sql = "select * people";    foos.add(createfoofromselect(sql)); }  private foo createfoofromselect(string sql){    foo foo;    sqlitecommand command = new sqlitecommand(sql, sqlconnection);    sqlitedatareader reader = command.executereader();    while(reader.read()){         yield return foo = new foo(reader["age"]);    } } 

you can use yield statement on methods return ienumerable<t>. in case method returns foo, cannot use yield statement there. instead can try such approach:

private ienumerable<foo> createfoofromselect(string sql){    sqlitecommand command = new sqlitecommand(sql, sqlconnection);    sqlitedatareader reader = command.executereader();    while(reader.read()){         yield return new foo(reader["age"]);    } } 

in case instead of using add can use addrange:

public list<foo> getfoos(){    list<foo> foos = new list<foo>();    string sql = "select * people";    foos.addrange(createfoofromselect(sql)); } 

you can read more yield keyword on msdn