Wrote complete patch code with hash checking and error handling.

Program.cs

@@ -1,12 +1,140 @@
 using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
+using System.IO;
+using System.Security.Cryptography;
 
 namespace TjcUsartHmiEnglishPatch {
     class Program {
+        const string fileName = "hmitype.dll";
+        const string fileNameBackUp = "hmitype.dll.original";
+        const string originalFileSha256 = "B8-47-93-94-75-68-5E-88-80-31-DD-60-D5-9C-7B-44-43-05-5E-98-C5-5A-CC-EA-1C-EB-90-45-D1-FB-B6-4E";
+        const string patchedFileSha256 = "03-CC-18-96-BF-E1-54-0A-B7-1B-F5-03-AE-FC-B9-FD-E2-54-4D-D4-80-25-F5-81-AD-F6-82-3F-F9-A5-F1-A0";
+
         static void Main(string[] args) {
+            try {
+
+                Console.WriteLine($"TJC USART HMI English Patch");
+                Console.WriteLine($"*** Make sure to run me as administrator! ***");
+                Console.WriteLine($"");
+                Console.WriteLine($"This program will try to locate and patch '{fileName}'.");
+                Console.WriteLine($"A backup of the original file will be created as '{fileNameBackUp}'.");
+                Console.WriteLine($"\nPress any key to continue...");
+                Console.ReadKey();
+
+                // Try and find the file automatically
+                Console.WriteLine($"\nTrying to locate '{fileName}'...");
+                var fp = GetFilePath();
+
+                // Let the user specify the file path
+                if (fp == null) {
+                    Console.WriteLine($"\nCould not find '{fileName}', please run this program from the same folder as '{fileName}' or paste the complete path now.");
+                    Console.Write($"\nPath to {fileName}: ");
+                    fp = Console.ReadLine().Trim();
+
+                    if (!File.Exists(fp)) {
+                        Console.WriteLine("\nThe file you entered doesn't exist. Exiting...");
+                        Console.WriteLine("\nPress any key to exit...");
+                        Console.ReadKey();
+                        return;
+                    }
+                }
+
+                var fInfo = new FileInfo(fp);
+
+                var fileData = File.ReadAllBytes(fInfo.FullName);
+                var hash = ComputeHash(fileData);
+
+                // Check if file is already patched
+                if (hash == patchedFileSha256) {
+                    Console.WriteLine($"\n'{fileName}' has already been patched! :)");
+                    Console.WriteLine("\nPress any key to exit...");
+                    Console.ReadKey();
+                    return;
+                }
+
+                // Check the original file hash
+                if (hash == originalFileSha256) {
+                    Console.WriteLine($"\n'{fileName}' has been located and the hash has been confirmed.");
+
+                    var backUpFile = Path.Combine(fInfo.DirectoryName, fileNameBackUp);
+                    if (!File.Exists(backUpFile)) {
+                        Console.WriteLine("\nCreating a backup...");
+                        File.Copy(fInfo.FullName, backUpFile);
+                        Console.WriteLine($"\nThe backup file '{fileNameBackUp}' has been created.");
+
+                        Console.WriteLine($"\nApplying patch to '{fileName}'...");
+                        var fileDataPatched = ApplyPatch(fileData);
+                        File.WriteAllBytes(fInfo.FullName, fileDataPatched);
+                        Console.WriteLine($"\nPatch was applied to '{fileName}'...");
+
+                        Console.WriteLine($"\nVerifying patch");
+
+                        var patchedFileHash = ComputeHash(File.ReadAllBytes(fInfo.FullName));
+                        if (patchedFileHash == patchedFileSha256) {
+                            Console.WriteLine($"\nPatch has been verified! :)");
+                            Console.WriteLine("\nPress any key to exit...");
+                            Console.ReadKey();
+
+                        } else {
+                            Console.WriteLine($"\nPatch could not be verified. Please restore '{fileName}' from '{fileNameBackUp}' and try again.");
+                            Console.WriteLine("\nPress any key to exit...");
+                            Console.ReadKey();
+                        }
+
+                    } else {
+                        Console.WriteLine($"\nThe backup file '{fileNameBackUp}' already exists.");
+                    }
+
+
+                } else {
+                    Console.WriteLine($"\n'{fileName}' hash is not correct, can't patch the file.");
+                    Console.WriteLine("\nPress any key to exit...");
+                    Console.ReadKey();
+                    return;
+                }
+
+            } catch (Exception e) {
+                Console.WriteLine("\n");
+                Console.WriteLine("An exception was caught:");
+                Console.WriteLine(e.Message);
+                Console.WriteLine("\nPress any key to exit...");
+                Console.ReadKey();
+            }
+        }
+
+        static byte[] ApplyPatch(byte[] data) {
+            data[0x00076766] = 0x17;
+            data[0x00076806] = 0x17;
+            data[0x0007689E] = 0x17;
+
+            return data;
+        }
+
+        static string ComputeHash(byte[] data) {
+            using (var cryptoProvider = new SHA256CryptoServiceProvider()) {
+                return BitConverter.ToString(cryptoProvider.ComputeHash(data));
+            }
+        }
+
+        static string GetFilePath() {
+            if (File.Exists(fileName)) {
+                return fileName;
+            }
+
+            var pf = Path.Combine(ProgramFilesx86(), "USART HMI", fileName);
+            if (File.Exists(pf)) {
+                return pf;
+            }
+
+            return null;
+        }
+
+        static string ProgramFilesx86() {
+            if (8 == IntPtr.Size
+                || (!string.IsNullOrEmpty(Environment.GetEnvironmentVariable("PROCESSOR_ARCHITEW6432")))) {
+                return Environment.GetEnvironmentVariable("ProgramFiles(x86)");
+            }
+
+            return Environment.GetEnvironmentVariable("ProgramFiles");
         }
     }
 }