I found that Ghostscript is able to convert PDF to Image format.
I tried PDF to Image Converter but not able to understand it clearly.
I have installed
You can use C# to run the GhostScript command line or use Platform Invoke (pInvoke) calls to call the GhostScript dll directly.
GhostScript is primarily file based, so the input is path to a file on disk and the output is the creation of files on disk. The parameters used to call either the dll or exe are basically the same, so there is not a huge benefit to calling the dll directly, but does make for nicer code.
I have C# wrapper that can be used to call the ghostscript dll, if you email me (address on profile) I will sent it to you.
HTH
UPDATE:
code repo moved to https://bitbucket.org/brightertools/ghostscript