plz help its a function to check file extension

byte[] ReadFile(string sPath)
        {
            //Initialize byte array with a null value initially.
            byte[] data = null;

            //Use FileInfo object to get file size.
            FileInfo fInfo = new FileInfo(sPath);
            try
            {
                if(fInfo.Extension == "jpg")
                {
                    long numBytes = fInfo.Length;

                    //Open FileStream to read file
                    FileStream fStream = new FileStream(sPath, FileMode.Open, FileAccess.Read);

                    //Use BinaryReader to read file stream into byte array.
                    BinaryReader br = new BinaryReader(fStream);

                    //When you use BinaryReader, you need to supply number of bytes to read from file.
                    //In this case we want to read entire file. So supplying total number of bytes.
                    data = br.ReadBytes((int)numBytes);
                    return data;
                }
                }
                catch (Exception ex)
                {
                    MessageBox.Show(ex.ToString());
                }
            }