Replace match string from string statement c#

Question

 string l_path = "C:\\Windows\\System32\\calc.exe"
 string findString = "C:\\Windows";

 if (l_path.Contains(findString )) // C:\\Windows\\System32\\calc.exe
 {
     string l_EnvironmentVariable = l_path.Replace(findString , "WinDir");
 }

I want to get exact match from string statement. But when I check contains method its checking for any character match.. result (l_EnvironmentVariable) should be like "WINDIR\System32\calc.exe"

Answer 1

Let's Split each path into its parts (SplitPath):

private static string[] SplitPath(string value) {
  Queue<string> parts = new Queue<string>();

  for (DirectoryInfo diValue = new DirectoryInfo(value);
       diValue != null;
       diValue = diValue.Parent)
    parts.Enqueue(diValue.Name);

  return parts.Reverse().ToArray();
}

And then we can operate with these parts (compare and modify):

string l_path = "C:\\Windows\\System32\\calc.exe";
string findString = "C:\\Windows";

var l_path_parts = SplitPath(l_path);
var findString_parts = SplitPath(findString);

// If l_path starts from findString
var startsFrom = l_path_parts
  .Zip(findString_parts, (a, b) => string.Equals(a, b, StringComparison.OrdinalIgnoreCase))
  .All(item => item);

string l_EnvironmentVariable = startsFrom 
  ? Path.Combine(
      new string[] { Environment.GetEnvironmentVariable("WinDir") }.Concat(l_path_parts
        .Skip(findString_parts.Length))
        .ToArray())
  : l_path; 

Console.Write(l_EnvironmentVariable);

Outcome: (depends on WinDir environment variable; if it's D:\Windows)

D:\Windows\System32\calc.exe

Please, note that we compare paths by their parts, and that's why

string l_path = "C:\\WindowsToTest\\System32\\calc.exe"; 

fails to match C:\\Windows (since WindowsToTest != Windows) and we'll get

l_EnvironmentVariable == C:\WindowsToTest\System32\calc.exe