First, you have to upgrade the firmware (I used v126.96.36.199 Beta 1 which can be found here. The detailed instructions about firmware upgrade are available at the same address.
Next, you have to solder ICSP pin on your Netduino board and connect D4 with D10 with jumper wire as it is shown on pictures below.
After adding the ICSP header and jumper wire, the hardware is ready and you can write a program to use the SD card reader. Below is the example I used for test and it worked fine.
public class Program
public static void Main()
StorageDevice.MountSD("SD", SPI.SPI_module.SPI1, Pins.GPIO_PIN_D10);
using (var filestream = new FileStream(@"SD\dontpanic.txt", FileMode.Create))
StreamWriter streamWriter = new StreamWriter(filestream);
streamWriter.WriteLine("This is a test of the SD card support on the netduino...This is only a test...");
using (var filestream = new FileStream(@"SD\dontpanic.txt", FileMode.Open))
StreamReader reader = new StreamReader(filestream);
The whole solution for Visual Studio 2010 can be found here