extracting contents of Datatable into list C#

Question

I am experimenting to take datatable contents into a list. I am using following code but its not working correctly.

public List<object> ShowMessage() { List<object> obj = new List<object>(); DataTable dt = new DataTable(); dt.Columns.Add("ID"); dt.Columns.Add("Name"); dt.Rows.Add("1","AAA"); dt.Rows.Add("2", "BBB"); dt.Rows.Add("3", "CCC"); foreach (DataRow dr in dt.Rows) { obj.Add(dr); } return obj; }

I am new and not sure I am doing in a right way or I need to use some thing else. Any suggestion will be highly appreciated.

Thanks.

What you are expecting to have in that list? Should it be list of strings "AAA", "BBB", "CCC" or something else? — Sergey Berezovskiy
– Sergey Berezovskiy, Commented Jan 10, 2014 at 13:37
@SergeyBerezovskiy yes, I am expecting a list of strings with "AAA", "BBB" and "CCC". — Kamran
– Kamran, Commented Jan 10, 2014 at 13:41
Side note - ShowMessage is not the best name for method which returns list of some data and doesn't show anything — Sergey Berezovskiy
– Sergey Berezovskiy, Commented Jan 10, 2014 at 13:41

Sergey Berezovskiy · Accepted Answer · 2014-01-10 13:42:38Z

Converting your DataTable to list of name strings (with help of Linq to DataSet):

List<string> names = dt.AsEnumerable().Select(r => r.Field<string>("Name")).ToList();

Which is same as

List<string> names = new List<string>(); foreach(DataRow r in dt.Rows) names.Add((string)r["Name"]);

Steve · Accepted Answer · 2014-01-10 13:45:41Z

I think you are making a too abstract example. This one use a possible class named Person

public class Person { public int PersonID; public string Name; // other fields will follow in future } public List<Person> GetPersonList() { List<Person> people = new List<Person>(); // This is just as example, because in real code // you get this table from a database DataTable dt = new DataTable(); dt.Columns.Add("ID"); dt.Columns.Add("Name"); dt.Rows.Add(1,"John"); dt.Rows.Add(2, "Mark"); dt.Rows.Add(3, "Steve"); // Loop over the rows and construct a Person instance for every row // Add that row to the List<Person> to return foreach (DataRow dr in dt.Rows) { Person p = new Person() {PersonID =Convert.ToInt32(dr[0]), Name = dr[1].ToString()); people.Add(p); } return people; }

By the way, this pattern of code, is exactly what a good ORM do for you. A little research for Entity Framework or Dapper would be very useful

Venkatesh Ellur · Accepted Answer · 2014-01-10 13:48:58Z

@Karni: you were close to what you need. however below is the modified version of your code example so that you achieve what you need..

public class Obj { public int ID { get; set; } public string Name { get; set; } } public class ListObj : List<Obj> { } class Program { static void Main(string[] args) { DataTable dt = new DataTable(); dt.Columns.Add("ID"); dt.Columns.Add("Name"); dt.Rows.Add("1", "AAA"); dt.Rows.Add("2", "BBB"); dt.Rows.Add("3", "CCC"); ListObj objListObj = new ListObj(); //to fill the list / collection for (int i = 0; i < dt.Rows.Count; i++) { objListObj.Add(new Obj() { ID = Convert.ToInt16(dt.Rows[i][0]), Name = dt.Rows[i][1].ToString() }); } //To verify if the collection is filled. foreach (var item in objListObj) { Console.WriteLine(item.ID + " : " + item.Name); } Console.Read(); } }

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