In C#, how can i the file extension from a byte[] audio files

You get mime type of a file using byte data. Could you please try on below , see if it works for you -

[DllImport(@"urlmon.dll", CharSet = CharSet.Auto)]
private extern static System.UInt32 FindMimeFromData(System.UInt32 pBC,
[MarshalAs(UnmanagedType.LPStr)] System.String pwzUrl,
[MarshalAs(UnmanagedType.LPArray)] byte[] pBuffer,
System.UInt32 cbSize, [MarshalAs(UnmanagedType.LPStr)] System.String pwzMimeProposed,
System.UInt32 dwMimeFlags,
out System.UInt32 ppwzMimeOut,
System.UInt32 dwReserverd);

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Anupam Maiti5y ago
You get mime type of a file using byte data. Could you please try on below , see if it works for you -
[DllImport(@"urlmon.dll", CharSet = CharSet.Auto)]
private extern static System.UInt32 FindMimeFromData(System.UInt32 pBC,
[MarshalAs(UnmanagedType.LPStr)] System.String pwzUrl,
[MarshalAs(UnmanagedType.LPArray)] byte[] pBuffer,
System.UInt32 cbSize, [MarshalAs(UnmanagedType.LPStr)] System.String pwzMimeProposed,
System.UInt32 dwMimeFlags,
out System.UInt32 ppwzMimeOut,
System.UInt32 dwReserverd);
byte[] document =<>;
file.InputStream.Read(document, 0, file.ContentLength);
System.UInt32 mimetype;
FindMimeFromData(0, null, document, 256, null, 0, out mimetype, 0);
System.IntPtr mimeTypePtr = new IntPtr(mimetype);
string mime = Marshal.PtrToStringUni(mimeTypePtr);
Marshal.FreeCoTaskMem(mimeTypePtr);

if (mime == "application/pdf")
{
    Response.Write("This is Valid File");
}
Sachin Singh5y ago
Byte[] only contains the file content and not the file type, if your web service doesn't expose Mime type (metadata) then you can't get it.
Better is to directly consult the author of the Webservice.