I’m trying to create a program which will search the xml files for nodes in the form <disp-formula id="deqnX-Y">, create a dictionary where key’s are like rid=”deqnX” … rid=”deqnY”, (where X is incremented by +1 till it reaches Y) and their respective value counterparts are like rid=”deqnX-Y” each, Then I can simply do a search and replace using the dictionary to change the link nodes. i.e. if the file has nodes like <disp-formula id="deqn5-7">, <disp-formula id="deqn9-10">, <disp-formula id="deqn3a-3c">, <disp-formula id="deqn4p-5b"> and there are link nodes in the form

<xref ref-type="disp-formula" rid="deqn5"> <xref ref-type="disp-formula" rid="deqn6"> <xref ref-type="disp-formula" rid="deqn10"> <xref ref-type="disp-formula" rid="deqn5c"> 

they should be changed to

<xref ref-type="disp-formula" rid="deqn5-7"> <xref ref-type="disp-formula" rid="deqn5-7"> <xref ref-type="disp-formula" rid="deqn9-10"> <xref ref-type="disp-formula" rid="deqn4p-5b"> 

I also want the program to ignore nodes like <disp-formula id="deqn5-7c"> and/or <disp-formula id="deqn2a-4"> in the file.

I’m using the below code for now

void Button1Click(object sender, EventArgs e)         {             string active_filename = "";             try             {                 string[] path = Directory.GetDirectories(textBox1.Text, "xml", SearchOption.AllDirectories)                     .SelectMany(x => Directory.GetFiles(x, "*.xml", SearchOption.AllDirectories)).ToArray();                 Dictionary<string, string> dict = new Dictionary<string, string>();                  var pat = new Regex(@"^deqn(\d+([a-z]+)?)-(\d+(?(2)[a-z]+))$  ");                 foreach (var file in path)                 {                     File.Copy(file,file+".bk",true);                       dict.Clear();                     active_filename = file;                     XDocument doc = XDocument.Load(file, LoadOptions.PreserveWhitespace);                     IEnumerable<XAttribute> list_of_elements = doc.Descendants("disp-formula").Where(z => (z.Attribute("id") != null) && pat.IsMatch(z.Attribute("id").Value)).Attributes("id");                     foreach (XAttribute ele in list_of_elements)                     {                         var m = Regex.Match((string) ele, pat.ToString());                         if (m.Success)                         {                             var X = m.Groups[1].Value;                             var Y = m.Groups[3].Value;                             int Xi, Yi;                             var isInt = int.TryParse(X, out Xi);                             if (isInt)                             {                             //for deqnX-Y where both X and Y are integers                                 Yi = int.Parse(Y);                                 for (int i = Xi; i <= Yi; i++)                                     dict.Add("rid=\"deqn" + i + "\"", "rid=\"" + ele.Value + "\"");                             }                             else                             {                             //for deqnX-Y where both X and Y are a combination of integer-alphabet                                 char startCharacter = X.Substring(X.Length - 1)[0];                                 char endCharacter = Y.Substring(Y.Length - 1)[0];                                 int startNumber = int.Parse(X.Substring(0, X.Length - 1));                                 int endNumber = int.Parse(Y.Substring(0, Y.Length - 1));                                 string alphabet = "abcdefghijklmnopqrstuvwxyz";                                 for (int i = startNumber; i <= endNumber; ++i)                                 {                                     int currentCharEnd =                                         (i == endNumber) ? alphabet.IndexOf(endCharacter) : alphabet.Length - 1;                                     for (int j = alphabet.IndexOf(startCharacter); j <= currentCharEnd; ++j)                                     {                                         dict.Add("rid=\"deqn" + i.ToString() + alphabet[j] + "\"",                                                  "rid=\"deqn" + X.ToString() + "-" + Y.ToString() + "\"");                                     }                                     startCharacter = 'a';                                 }                             }                         }                            string text = File.ReadAllText(file);                         foreach (KeyValuePair<string, string> element in dict)                         {                             //do a search all replace all (search Key and replace by Value                             text = text.Replace(element.Key, element.Value);                         }                         File.WriteAllText(file, text);                       }                 }                 MessageBox.Show("Done");             }             catch (Exception ex)             {                  MessageBox.Show(string.Format(@"Error in file ({0}), below are the debug details: {1}", active_filename, ex.StackTrace.ToString()));             } 

Is it possible to make the program more efficient? If so how can I do that?

Will changing

foreach (KeyValuePair<string, string> element in dict)                         {                         text = text.Replace(element.Key, element.Value);                         } 

by

Parallel.ForEach(dict, element =>                         {                             text = text.Replace(element.Key, element.Value);                         } ); 

make any substantial difference?