how can we check any file is password protect or not in c#

There is a Nuget package for System.IO.Packaging. I do not know if it is necessary to install that package. When I install it I then get an error saying PackageRelationshipTypes does not exist. Intellisense says I need to install an NPOI package and there are multiple NPOI packages. Therefore if the code provided by Rajkiran Swain works then I think we need an explanation of how to get the System.IO.Packaging namespace.

Hi naimish your code is not working

@rajkiran code is not working  keyword PackageRelationshipTypes is unknown

Try below method:

public static bool IsPasswordProtected(string filePath, string password)
{
    try
    {
        using (FileStream fileStream = new FileStream(filePath, FileMode.Open))
        {
            // Try to open the file with the provided password
            using (StreamReader streamReader = new StreamReader(fileStream, false))
            {
                streamReader.ReadToEnd(); // Read the file to validate the password
            }
        }

        // If the file was successfully opened and read, it is not password-protected
        return false;
    }
    catch (SecurityException)
    {
        // The file is password-protected
        return true;
    }
    catch (Exception)
    {
        // An exception occurred, which might indicate that the file is password-protected
        return true;
    }
}

Thanks

using System.IO;
using System.IO.Packaging;

public bool IsFilePasswordProtected(string filePath)
{
    try
    {
        using (Package package = Package.Open(filePath, FileMode.Open, FileAccess.Read))
        {
            // Check if the package contains the encryption package relationship
            if (package.RelationshipExists(PackageRelationshipTypes.Encryption))
            {
                return true; // File is password protected
            }
        }
    }
    catch (IOException)
    {
        // Handle any IO exceptions
    }
    catch (System.Security.Cryptography.CryptographicException)
    {
        // Handle cryptographic exceptions
    }

    return false; // File is not password protected or an error occurred
}