Check a valid file using magic check

Question

I am using this source code to check the whether a PDF file is valid.

string contenttype = String.Empty;

            Stream checkStream = fUploadAttachment1.PostedFile.InputStream;

            BinaryReader chkBinary = new BinaryReader(checkStream);
            Byte[] chkbytes = chkBinary.ReadBytes(0x10);

            string data_as_hex = BitConverter.ToString(chkbytes);
            string magicCheck = data_as_hex.Substring(0, 11);

            //Set the contenttype based on File Extension
            switch (magicCheck)
            {
                case "FF-D8-FF-E1":
                    contenttype = "image/jpg";
                    break;
                case "FF-D8-FF-E0":
                    contenttype = "image/jpeg";
                    break;
                case "25-50-44-46":
                    contenttype = "text/pdf";
                    break;
            }
            if (contenttype != String.Empty)
            {
                Byte[] bytes = chkBinary.ReadBytes((Int32)checkStream.Length);
                lblMsgBox1.Text = "Uploaded File is of type " + contenttype;
                lblMsgBox1.ForeColor = System.Drawing.Color.Green;
            }
            else
            {
                lblMsgBox1.Text = "Please Upload Valid File with Original extension";
                lblMsgBox1.ForeColor = System.Drawing.Color.Red;
            }

I want to perform a similar check for word document too. How can I do that?

Answer 1

Hi @Adeel Mirza ,
You can get the magic number of the file type you want in the file signature list, so you just need to add a condition.
https://en.wikipedia.org/wiki/List_of_file_signatures

 case "50-4B-03-04":  
        contenttype = "text/word";  
        break;  

Best regards,
Lan Huang

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