January 30, 2011

LINQ on DataTable

How to works with Linq on DataTable
How LINQ works with DataTable
Why we can not query against the DataTable's Rows collection?
I can not find AsEnumerable() in my DataTable

Sample
DataTable Student = new DataTable("Student"); 
Student.Columns.Add("Name", typeof(String)); 
Student.Columns.Add("Date", typeof(DateTime)); 
Student.Columns.Add("NO", typeof(Int32)); 
Student.Rows.Add(new object[] {"A1",Convert.ToDateTime("2010/01/01"),0}); 
Student.Rows.Add(new object[] {"A2",Convert.ToDateTime("2011/01/01"),0}); 
Student.Rows.Add(new object[] {"A3",Convert.ToDateTime("2009/01/01"),1}); 
Student.Rows.Add(new object[] {"A4",Convert.ToDateTime("2012/01/01"),1}); 
Student.Rows.Add(new object[] {"A5",Convert.ToDateTime("2011/01/01"),1}); 
Student.Rows.Add(new object[] {"A6",Convert.ToDateTime("2011/01/01"),2}); 
Student.Rows.Add(new object[] {"A7",Convert.ToDateTime("2011/01/01"),2}); 

// Linq Query 
var query = from rows 
            in Student.AsEnumerable() 
            where rows["NO"].Equals(1) 
            orderby rows["Date"] descending 
            select rows; 

// A 
DataTable result = query.CopyToDataTable(); 
MessageBox.Show(result.Rows[0][0].ToString()); 

// B 
MessageBox.Show(query.AsDataView()[0][0].ToString());



PS: If you want to use of LINQ to DataSet as ORM you can used of ToQueryable() instead of AsEnumerable().
PS: If you want to use of EF (ADO.NET Entity Framework) as ORM you can directrly use of your Table instead of ToQueryable() or AsEnumerable()

3 comments:

Athena said...

I can't use this one , bcz I didn't have AsEnumerable() in my code , why should I do now?
I had using System.Data.Linq.

AmirMehdi KhademAstaneh said...

Dear Athena,
Please share your both of codes and errors here. those're required for your help.

AmirMehdi KhademAstaneh said...

@Athena: it would help you with ToList() like bellow:
var x = (from y in z select y).ToList();