Displaying Files of Unknown Types Stored in SQL Server Using C# WPF

zenvo st

2y763C#

I am developing a C# WPF application using .NET 6 in Visual Studio 2022, with a SQL Server 2008 R2 database. My database contains a table GRADE_CUST_GRP with a column GCPS of type image, where files of various types are stored without any file extension information. I am looking for a way to retrieve and open these files in a WPF application, similar to how "SQL Image Viewer" dynamically displays content based on the file's actual type (e.g., displaying an image for picture files, or opening a document for PDF/text files), without prior knowledge of the file type. The challenge is to detect the file type from the byte content and then display or open the file appropriately in the WPF application. I am open to using third-party libraries or any .NET functionality that could help achieve this. However, attempts to use the MimeType class for recognizing the file type were unsuccessful, as it did not recognize the file type correctly. Here is the SQL definition for the relevant part of the table:

CREATE TABLE [dbo].[GRADE_CUST_GRP]
(
    [GCGRPID] [int] NOT NULL,
    [GCPS] [image] NULL
)

How can I achieve the functionality of opening and viewing files directly from the database in my WPF application, regardless of their type, as "SQL Image Viewer" does? Any suggestions for libraries or approaches for detecting file types and handling them appropriately in WPF would be greatly appreciated, especially considering the limitations I encountered with the MimeType class and the diverse file types, including OLE Object packages. (From MS Access) Please provide code examples or guidance on how to implement this feature.

PS : This is a challenge that I have to do for a very old project

Also I think soe of data are undetectable becuase of this :
// Example offset - this may need to be adjusted based on the actual OLE container format
const int oleHeaderOffset = 78;

2 Replies

Know the answer? Post it — somebody with the same question will find it here.

zenvo st2y ago

    public static string ExtractFileExtension(byte[] byteyFile)
    {
        // Define a regular expression to find patterns that look like file extensions
        // This regex looks for a dot followed by 2-5 alphanumeric characters, possibly at the end of a string or followed by a non-alphanumeric character.
        Regex regex = new Regex(@"\.\w{2,5}($|\W)", RegexOptions.IgnoreCase);

        // Try different encodings to convert the byte array to a string
        Encoding[] encodings = { Encoding.UTF8, Encoding.Unicode, Encoding.ASCII };
        foreach (var encoding in encodings)
        {
            string fileContentAsString = encoding.GetString(byteyFile);
            Match match = regex.Match(fileContentAsString);
            if (match.Success)
            {
                // If a match is found, clean it up and return the extension
                string extension = match.Value.Trim(new char[] { '.', ' ', '\0', '\r', '\n', '\t', (char)0xFFFD });
                return extension.Split(new char[] { ' ', '\0', '\r', '\n', '\t', (char)0xFFFD }, StringSplitOptions.RemoveEmptyEntries)[0];
            }
        }

        // If no extension is found, return null or an empty string
        return null;
    }

Interestingly, with the help of AI, I was able to get the file extension from the bytes themselves (even OLE object) or even a file with a fake extension.

Sam Hobbs2y ago
Someone else (or maybe you) posted the same question in the Microsoft Q&A; see:

Displaying Files of Unknown Types Stored in SQL Server Using C# WPF - Microsoft Q&A
https://learn.microsoft.com/en-us/answers/questions/1578011/displaying-files-of-unknown-types-stored-in-sql-se

My guess is that the developers of SQL Image Viewer from Yohz Software have spent much time figuring out how to recognize each of the formats. There is probably not an easy way to do it.
+1