ADO.NET: How can we update a DataTable column values as fast as calculated columns does? - ado.net

Question

I have a small test program that creates a DataTable with 1M rows.
Then I add a calculated column (Expression column), it's super fast like a second.
Then I just try to add a new column and set values to it, it takes more than 10 seconds.
DataTable update is slow. How can I make it as fast as calculated column?
10 seconds does seem acceptable but that is just a test program to show the difference.
This can become worst depending on how many rows, columns, etc.
Anyway if calculated column is able to do it that fast, hopefully we can get same performance with normal updates.
It seems calculated columns is able to turn off some notifications or other things. I'm not sure.
Any idea? Advice? Maybe I'm missing something when updating the DataTable.
Thanks in advance
Below is the code sample I'm using:
using System;
using System.Data;
namespace Test1
{
class Program
{
static void Main(string[] args)
{
try
{
System.Diagnostics.Stopwatch watch = new System.Diagnostics.Stopwatch();
watch.Start();
Console.WriteLine("DataTable creation started ...");
DataTable data = new DataTable();
int nbrCols = 50;
for (int i = 0; i < nbrCols; i++)
{
data.Columns.Add(string.Concat("COL_", (i + 1)), typeof(double));
}
System.Random r = new System.Random();
data.BeginLoadData();
int nbrows = 1000000;
for (int i = 0; i < nbrows; i++)
{
DataRow newRow = data.NewRow();
for (int j = 0; j < nbrCols; j++)
{
newRow[j] = r.NextDouble();
}
data.Rows.Add(newRow);
}
data.EndLoadData();
watch.Stop();
Console.WriteLine("DataTable creation = " + watch.ElapsedMilliseconds / 1000.0);
int colIndexFlow1 = data.Columns.IndexOf("COL_1");
int colIndexFlow2 = data.Columns.IndexOf("COL_2");
/* Add a calculated columns */
watch.Restart();
data.Columns.Add("CALC_1", typeof(double), "COL_1 + COL_2");
data.AcceptChanges();
watch.Stop();
Console.WriteLine("Calculated Column creation = " + watch.ElapsedMilliseconds / 1000.0);
/* Add a new column */
watch.Restart();
data.BeginLoadData();
data.Columns.Add("NEW_1", typeof(double));
int colIdx = data.Columns.IndexOf("NEW_1");
foreach (DataRow row in data.Rows)
{
//double val = row.Field<double>("COL_1") + row.Field<double>("COL_2");
//row.SetField<double>(colIdx, val);
// Most of the time is spent to actually set the data
// Question is how can we make the update happening as fast as the update done when using a calculated column.
row.SetField<double>(colIdx, 2.0);
}
data.AcceptChanges();
data.EndLoadData();
watch.Stop();
Console.WriteLine("New Column creation = " + watch.ElapsedMilliseconds / 1000.0);
}
catch (Exception ex)
{
Console.WriteLine("Error=" + ex.Message);
}
finally
{
Console.ReadLine();
Console.WriteLine("Press any key to exit");
}
}
}
}