string sqlAllCustomers = "SELECT * FROM Customers";
string cnStr = 
  @"Data Source=.;Initial Catalog=northwind;Integrated Security=True";

using (SqlConnection cn = new SqlConnection(cnStr))
{
    cn.Open();
    SqlCommand cmd = new SqlCommand(sqlAllCustomers, cn);
    SqlDataAdapter adpt = new SqlDataAdapter(cmd);
    DataTable dtCust1 = new DataTable("Customers");
    adpt.Fill(dtCust1);
    dtCust1.PrimaryKey = new DataColumn[]{dtCust1.Columns["CustomerID"]};

    DataTable dtCust2 = dtCust1.Clone();
    DataRow row1 = dtCust2.NewRow();
    row1["CustomerID"] = "ALFKI";
    row1["CompanyName"] = "Some Company";
    dtCust2.Rows.Add(row1);

    DataRow row2 = dtCust2.NewRow();
    row2["CustomerID"] = "FOO";
    row2["CompanyName"] = "Some Other Company";
    dtCust2.Rows.Add(row2);

    DataSet ds = new DataSet("MySillyDataSet");
    ds.Tables.Add(dtCust1);
    ds.Merge(dtCust2);

    dgTest.DataSource = dtCust1;
}

using (SqlConnection cn = new SqlConnection(cnStr))
{
    // Create the Command and Adapter
    SqlCommand cmd = new SqlCommand(sqlAllCustomers, cn);
    SqlDataAdapter adpt = new SqlDataAdapter(cmd);

    // Create a DataTable and fill it 
    DataTable dtCustomers = new DataTable("Customers");
    adpt.Fill(dtCustomers);

    DataSet ds = new DataSet();
    ds.Tables.Add(dtCustomers);
    adpt.SelectCommand = new SqlCommand("SELECT * FROM Orders", cn);
    adpt.Fill(ds, "Orders");

    // Create the DataTableReader (it is disconnected)
    using(DataTableReader dtRdr = dtCustomers.CreateDataReader())
    {
        do
        {
            Console.WriteLine("******************************");
            while (dtRdr.Read())
            {
                Console.WriteLine(dtRdr.GetValue(0).ToString());
            }
        }
        while (dtRdr.NextResult());
    }
}

using (SqlConnection cn = new SqlConnection(cnStr))
{
    SqlCommand cmd = new SqlCommand(sqlAllCustomers, cn);
    SqlDataAdapter adpt = new SqlDataAdapter(cmd);
    DataTable dtCustomers = new DataTable("Customers");
    adpt.Fill(dtCustomers);
    dtCustomers.PrimaryKey = new DataColumn[] { 
        dtCustomers.Columns["CustomerID"] };

    // Pause here to execute this SQL directly against the database:
    // UPDATE Customers SET City = 'Miami' WHERE CustomerID = 'ALFKI'
    System.Diagnostics.Debugger.Break();

    // Change the CURRENT values in the DataTable
    DataRow row = dtCustomers.Rows.Find("ALFKI");
    row["City"] = "Somewhere";
    // ORIGINAL city == Berlin 
    // CURRENT  city == New York
    DisplayDataRowVersions(row, "Immediately after I change the City" +
        " from Berlin to New York", "City");

    // Load another DataTable with customer data.
    DataTable dtCustomers2 = new DataTable("Customers");
    adpt.Fill(dtCustomers2);
    DataTableReader dtRdrCustomers = dtCustomers2.CreateDataReader();

    LoadOption opt = LoadOption.PreserveChanges;
    switch (opt)
    {
        case LoadOption.OverwriteChanges:
            // Overwrite ORIGINAL and Overwrite CURRENT values
            dtCustomers.Load(dtRdrCustomers, LoadOption.OverwriteChanges);
            // ORIGINAL city == Miami
            // CURRENT  city == Miami
            row = dtCustomers.Rows.Find("ALFKI");
            ShowVersions (row, 
                "Immediately after LoadOptions.OverwriteChanges", 
                "City");
            break;
        case LoadOption.Upsert:
            // Keep ORIGINAL and Overwrite CURRENT values
            dtCustomers.Load(dtRdrCustomers, LoadOption.Upsert);
            // ORIGINAL city == Berlin 
            /// CURRENT  city == Miami 
            row = dtCustomers.Rows.Find("ALFKI");
            ShowVersions (row, 
                "Immediately after LoadOptions.Upsert", "City");
            break;
        case LoadOption.PreserveChanges:
            // Overwrite    ORIGINAL and    Keep        CURRENT values
            dtCustomers.Load(dtRdrCustomers, LoadOption.PreserveChanges);
            // ORIGINAL city == Miami
            // CURRENT  city == New York
            row = dtCustomers.Rows.Find("ALFKI");
            ShowVersions (row, 
                "Immediately after LoadOptions.PreserveChanges", "City");
            break;
    }
}

DataTable dtCustomers = new DataTable("Customers");

using (SqlConnection cn = new SqlConnection(cnStr))
{
    SqlCommand cmd = new SqlCommand(sqlAllCustomers, cn);
    SqlDataAdapter adpt = new SqlDataAdapter(cmd);
    adpt.Fill(dtCustomers);
    dtCustomers.PrimaryKey = new DataColumn[] { 
        dtCustomers.Columns["CustomerID"] };
}

// Change the RowState of a few rows
DataRow row = dtCustomers.Rows.Find("ALFKI");
row.SetModified();
row = dtCustomers.Rows.Find("BOLID");
row.SetModified();
row = dtCustomers.Rows.Find("ANTON");
row.SetAdded();

int modRows = dtCustomers.GetChanges(
    DataRowState.Modified).Rows.Count;
int addRows = dtCustomers.GetChanges(DataRowState.Added).Rows.Count;

StringBuilder bldr = new StringBuilder();
bldr.Append(modRows.ToString());
bldr.Append(" row(s) were modified.");
bldr.Append(Environment.NewLine);
bldr.Append(addRows.ToString());
bldr.Append(" row(s) were added");
MessageBox.Show(bldr.ToString());

DataTable dt = new DataTable("foo");
DataColumn pkCol = new DataColumn("ID", Type.GetType("System.Int32"));
pkCol.AutoIncrement = true;
pkCol.AutoIncrementSeed = 1;
pkCol.AutoIncrementStep = 1;
dt.Columns.Add(pkCol);
dt.PrimaryKey = new DataColumn[] { pkCol };
dt.Columns.Add("SomeNumber", Type.GetType("System.Int32"));
dt.Columns["SomeNumber"].Unique = true;

int limit = 1000000;
int someNumber = limit;
DateTime startTime = DateTime.Now;
for (int i = 1; i <= limit; i++)
{
    DataRow row = dt.NewRow();
    row["SomeNumber"] = someNumber—;
    dt.Rows.Add(row);
}
TimeSpan elapsedTime = DateTime.Now - startTime;
MessageBox.Show(dt.Rows.Count.ToString() + 
    " rows loaded in " + elapsedTime.TotalSeconds + " seconds.");