DataTable table = new DataTable("DGV_SelectedRows");
foreach(DataGridViewColumn column in dataGridView1.Columns)
table.Columns.Add(column.Name, typeof(string));
for(int i=0;i<dataGridView1.SelectedRows.Count; i++)
{
table.Rows.Add();
for(int j=0;j<dataGridView1.Columns.Count; j++)
{
table.Rows[i][j] = dataGridView1[j,i].Value;
}
}