c# 文件MD5码 比较,检测文件是否一样（附源码）

【核心代码】

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Security.Cryptography;
using System.IO;
using System.Threading;

namespace FileMD5 {
    public partial class MainForm : Form {
        public MainForm() {
            InitializeComponent();
        }

        private void button_file_Click(object sender, EventArgs e) {
            OpenFileDialog fileDialog = new OpenFileDialog();
            fileDialog.Title = "请选择文件";
            fileDialog.RestoreDirectory = true;

            if (fileDialog.ShowDialog() == DialogResult.OK) {
                textBox_file.Text = fileDialog.FileName;
                textBox_result.Text = "";
                FileInfo file = new FileInfo(fileDialog.FileName);
                fileSzie = file.Length;
                showFilesize(fileSzie);
            }

        }

        private void button_exit_Click(object sender, EventArgs e) {
            this.Close();
            this.Dispose();
        }

        private void button_check_Click(object sender, EventArgs e) {
            checkResult();
        }

        MD5 md5 = (MD5)CryptoConfig.CreateFromName("MD5");
        long fileSzie = 0;

        private void button_calc_Click(object sender, EventArgs e) {
            string file = textBox_file.Text;

            if (file.Length == 0) {
                textBox_result.Text = "请先重新选择文件!";
                return;
            }

            FileStream fs = null;
            try {
                fs = new FileStream(file, FileMode.Open, FileAccess.Read);
            } catch (SystemException) {
                textBox_result.Text = "文件打开错误,请重新选择文件!";
                return;
            }

            //对于大于 100M 的文件启用多线程
            if (fs.Length > 100L * 1024 * 1024) {

                string message = "文件已经超过 100M ，需要较长的计算时间。\n软件将启动后台线程进行处理。是否继续？";
                string caption = "文件较大";
                MessageBoxButtons buttons = MessageBoxButtons.YesNo;

                if (MessageBox.Show(message, caption, buttons) == System.Windows.Forms.DialogResult.No) {
                    fs.Close();
                    textBox_result.Text = "文件较大，未计算。";
                    return;
                }
                textBox_result.Text = "正在计算中，请稍候......";
                button_calc.Enabled = false;
                button_file.Enabled = false;

                Thread thread = new Thread(new ParameterizedThreadStart(calcMD5));
                thread.Start(fs);

            } else {
                calcMD5(fs);
            }
        }

        //建立一个 object 参数的函数，是为了处理线程调用中，使用参数的问题。
        private void calcMD5(object fs) {
            calcMD5((FileStream)fs);
        }

        // Invoke 函数需要使用的委托
        delegate void updateWindows(byte[] result);

        private void calcMD5(FileStream fs) {
            byte[] md5byte = md5.ComputeHash(fs);

            if (this.InvokeRequired) {
                this.Invoke(new updateWindows(showResult), md5byte);
            } else {
                showResult(md5byte);
            }
            fs.Close();
        }

        private void showResult(byte[] md5byte) {
            int i, j;
            StringBuilder sb = new StringBuilder(32);
            foreach (byte b in md5byte) {
                i = Convert.ToInt32(b);
                j = i >> 4;
                sb.Append(Convert.ToString(j, 16));
                j = ((i << 4) & 0x00ff) >> 4;
                sb.Append(Convert.ToString(j, 16));
            }

            String result = sb.ToString().ToUpper();

            textBox_result.Text = result;
            button_calc.Enabled = true;
            button_file.Enabled = true;
            checkResult();
            
        }

        private void checkResult() {

            string result = textBox_result.Text;

            if (textBox_md5.Text.Length == 0) {
                textBox_compare.Text = "";
                textBox_compare.Visible = false;
                return;
            }
            
            if(result.Length != 32 ) {
                textBox_compare.Visible = true;
                textBox_compare.BackColor = Color.Pink;
                textBox_compare.Text = "计算结果框中不是MD5码，请先进行计算！";
                return;
            }

            if (textBox_md5.Text.Trim().ToUpper().Equals(result.ToUpper())) {
                textBox_compare.Visible = true;
                textBox_compare.BackColor = Color.LightGreen;
                textBox_compare.Text = "MD5码 已匹配，文件未被修改，可放心使用！";
            } else {
                textBox_compare.Visible = true;
                textBox_compare.BackColor = Color.Red;
                textBox_compare.Text = "MD5码 不匹配，文件已被修改，请小心！";
            }
        }

        private void showFilesize(long size) {
            
            float d_size;
            string unit = "Byte";

            if (size > 1024 * 1024 * 1024) {    //大于 1G 的显示
                d_size = size / (float)(1024 * 1024 * 1024);
                unit = "GB";
            } else {
                if (size > 1024 * 1024) {    //大于 1M 的显示
                    d_size = size / (float)(1024 * 1024);
                    unit = "MB";
                } else {
                    if (size > 1024) {    //大于 1K 的显示
                        d_size = size / (float)(1024);
                        unit = "KB";
                    } else {
                        d_size = size;
                    }
                }
            }
            textBox_filesize.Text = string.Format(" {0:F} {1} ( {2:N0}字节 )", d_size, unit, size);
        }
    }
}