how to retrieve minimum date from a datatable column using linq

DateTime minimunDate =  dtCollegeDetails.Rows.OfType<datarow>().Select(k => Convert.ToDateTime(k["penalty_date"])).OrderBy(k => k).First(); 

DateTime minimunDate = dtCollegeDetails.Rows.OfType<DataRow>().Select(k => Convert.ToDateTime(k["penalty_date"])).Min();

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data;

namespace Date
{
    class Program
    {
        static void Main(string[] args)
        {
            DataTable dt = new DataTable();
            dt.Columns.Add(new DataColumn("PaymentDate", typeof(DateTime)));
            dt.Columns.Add(new DataColumn("Payment", typeof(int)));

            DataRow dr = dt.NewRow();
            dr["PaymentDate"] = new DateTime(2012,10,12);
            dr["Payment"] = 1200;
            dt.Rows.Add(dr);

             dr = dt.NewRow();
             dr["PaymentDate"] = new DateTime(2013, 10, 24);
            dr["Payment"] = 1200;
            dt.Rows.Add(dr);

             dr = dt.NewRow();
             dr["PaymentDate"] = new DateTime(2013, 11, 23);
            dr["Payment"] = 1200;
            dt.Rows.Add(dr);
//Method 1 using dataview
            DataView dv = dt.DefaultView;
            dv.RowFilter = "PaymentDate=Min(PaymentDate)";
            
            Console.WriteLine(string.Format("The Payment is {0} on {1}", dv[0][1], dv[0][0]));

// Method 2 using Linq
            DateTime drLatesPayment = (DateTime)dt.Rows.OfType<datarow>().Min( r => r["PaymentDate"]);

            Console.WriteLine(string.Format("The Payment is on {0}", drLatesPayment));    
            Console.Read();
        }
    }


}