how to swap the high-byte and the low-byte?

there is a binary file in unix OS, I want to read it at windows OS, there must be to swap the byte sequence of the int or float type data. to int, with follow code: " short n; short i,j,k=0x00ff; i=n<<8; j=n>>8; j=j&k; n=i|j; " compile with error: " can not convert type 'int' to type 'short' " why? how about float to be swapped? in c++, that is easy! we just do it with union! like this " void TransFloat(float *f) { union { float i; unsigned char c[4]; } a; unsigned char tmp; a.i=*f; tmp=a.c[0]; a.c[0]=a.c[3]; a.c[3]=tmp; tmp=a.c[1]; a.c[1]=a.c[2]; a.c[2]=tmp; *f=a.i; return; } " but in c#, swap float type data may be difficult, somebody can help me? thx!