一个简单的文件MD5码自动计算比较器（附源码）

主要对 多线程更新 winform 不是特别清楚，绕来绕去，搞得很晕乎，主要代码如下， 还请各位大侠多多指点，谢谢！

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);
         }
     }
 }

完整的 vs2010 项目下载：http://xiazai.jb51.net/201302/yuanma/filemd5_jb51.net.rar