how can I convert a float array to Byte array

This is called serialization. You apparently need binary serialization into array of bytes used for many purposes. You need to use the class System.BitConverter, http://msdn.microsoft.com/en-us/library/system.bitconverter.aspx[^].

It allows you to convert to byte a single float element using GetBytes(Single) or GetBytes(Double).

To do the whole thing, you need first serialize the length of the float array using GetBytes(Int32), then serialize all float members in loop and concatenate all together (for example, use Array.Copy). Pre-create the resulting array at once with the length sizeof(Int32) + ArrayLength*sizeof(Double) (or sizeof(Single)).

You will probably need to right a matching deserialization method — from array of byte to array of float (using ToInt32, ToDouble or ToSingle).

—SA