Convert float to string without losing precision

I want to store a float value into string without lossing or adding any single precision digits.

For example if my float value is 23.345466467 , I want my string to have str = "23.345466467" exact digits.

I tried using CString format function with %f. Its giving only first 6 precision. or if i use %10 , if my float value is having less than 10 precision,its adding some more junk precision. I want to get exact float value into my string. how to do this?