How to bulk insert efficiently

To insert a generic list it must be converted to a DataTable:

public static DataTable ConvertToDataTable<T>(IList<T> list)
{
    PropertyDescriptorCollection propertyDescriptorCollection = TypeDescriptor.GetProperties(typeof(T));
    DataTable table = new DataTable();
    for (int i = 0; i < propertyDescriptorCollection.Count; i++)
    {
        PropertyDescriptor propertyDescriptor = propertyDescriptorCollection[i];
        Type propType = propertyDescriptor.PropertyType;
        if (propType.IsGenericType && propType.GetGenericTypeDefinition() == typeof(Nullable<>))
        {
            table.Columns.Add(propertyDescriptor.Name, Nullable.GetUnderlyingType(propType));
        }
        else
        {
            table.Columns.Add(propertyDescriptor.Name, propType);
        }
    }
    object[] values = new object[propertyDescriptorCollection.Count];
    foreach (T listItem in list)
    {
        for (int i = 0; i < values.Length; i++)
        {
            values[i] = propertyDescriptorCollection[i].GetValue(listItem);
        }
        table.Rows.Add(values);
    }
    return table;
}

Then the SqlBulkCopy can be used. In the example the user table is bulk inserted:

DataTable dt = new DataTable();
using (SqlConnection connection = new SqlConnection(connectionString))
{
    connection.Open();
    using (SqlBulkCopy sqlBulkCopy = new SqlBulkCopy(connection))
    {
        sqlBulkCopy.ColumnMappings.Add("UserID", "UserID");
        sqlBulkCopy.ColumnMappings.Add("UserName", "UserName");
        sqlBulkCopy.ColumnMappings.Add("Password", "Password");
        sqlBulkCopy.DestinationTableName = "User";
        sqlBulkCopy.WriteToServer(dt);
    }
}