Interesting Question on C#

Question

I have one problem related to double data type .

dou=0.0000454444
when i convert this to string it shows the value in exponential like this
messagebox.show(dou.ToString)
it shows the value in 4.5 e-4 in exponential .
Value is changing in run time even i do not cross the precision of double .I want to be my answer in double format .
Anyone know this problem please help me .I have applied all things.