[c#] Convert double to string

i have three double variable a ,b and c

a = 0.000006 
b = 6 
c = a/b;

so C should be 0.000001

i want to show this value in text box so i wrote

textbox.text = c.tostring();

but it's give result as "1E-06"..

Can anybody help me out how can i put correct value in textbox ?

Thanks

Try c.ToString("F6");

(For a full explanation of numeric formatting, see MSDN)