[c#] byte array to pdf

I am trying to convert content of a file stored in a sql column to a pdf.

I use the following piece of code:

byte[] bytes;
BinaryFormatter bf = new BinaryFormatter();
MemoryStream ms = new MemoryStream();
bf.Serialize(ms, fileContent);
bytes = ms.ToArray();
System.IO.File.WriteAllBytes("hello.pdf", bytes);

The pdf generated is corrupt in the sense that when I open the pdf in notepad++, I see some junk header (which is same irrespective of the fileContent). The junk header is NUL SOH NUL NUL NUL ....

Usually this happens if something is wrong with the byte array.

File.WriteAllBytes("filename.PDF", Byte[]);

This creates a new file, writes the specified byte array to the file, and then closes the file. If the target file already exists, it is overwritten.

Asynchronous implementation of this is also available.

public static System.Threading.Tasks.Task WriteAllBytesAsync 
(string path, byte[] bytes, System.Threading.CancellationToken cancellationToken = null);