C# Verifying digital signature in .xlsx and .docx files (1874613)

I need one web application developed in c# ([ASP.NET][1]), using only classes from .Net Framework API, without use of API of other commercial companies. Description: Necessary files are .xlsx and .docx files (MS Office 2007 and 2010) The user should be able to choose a file with FileChooser. After choosing of a file: --- if a document does not contain a digital signature, the program should report about this to the user (Warning). --- if a document contains a digital signature, the program must read data of digital signature and of Certificate and must inform the folowing data to the users: 1) Who signed the document; 2) Date of signature; 3) Which organization issued a certificate; 4) Validity of a certificate; 5) Status of the digital signature I want to buy SourceCode of this web application. The SourceCode must be written clearly and distinctly.I want to integrate this web application into my website