cannot read the data from arduino to the c#

Using Arduino Interfacing w/ Software on the Computer
33

this is my snippet of coding for arduino..

float rate, waterlevel,longitude,latitude;
...if (latitude== 3.8463 && longitude==103.3059)
{serial.print("latitude:");
serial.println(latitude,4);
serial.print("longitude:");
serial.println(longitude,4);

why i cannot pun the value of latitude and longitude into the label on the winform?