Why does Path.Combine not properly concatenate filenames that start with Path.DirectorySeparatorChar?

by

This is kind of a philosophical question (which perhaps only Microsoft can truly answer), since it’s doing exactly what the documentation says.

System.IO.Path.Combine

“If path2 contains an absolute path, this method returns path2.”

Here’s the actual Combine method from the .NET source. You can see that it calls CombineNoChecks, which then calls IsPathRooted on path2 and returns that path if so:

public static String Combine(String path1, String path2) {
    if (path1==null || path2==null)
        throw new ArgumentNullException((path1==null) ? "path1" : "path2");
    Contract.EndContractBlock();
    CheckInvalidPathChars(path1);
    CheckInvalidPathChars(path2);

    return CombineNoChecks(path1, path2);
}

internal static string CombineNoChecks(string path1, string path2)
{
    if (path2.Length == 0)
        return path1;

    if (path1.Length == 0)
        return path2;

    if (IsPathRooted(path2))
        return path2;

    char ch = path1[path1.Length - 1];
    if (ch != DirectorySeparatorChar && ch != AltDirectorySeparatorChar &&
            ch != VolumeSeparatorChar) 
        return path1 + DirectorySeparatorCharAsString + path2;
    return path1 + path2;
}

I don’t know what the rationale is. I guess the solution is to strip off (or Trim) DirectorySeparatorChar from the beginning of the second path; maybe write your own Combine method that does that and then calls Path.Combine().

More Related Contents:

  1. Is there a way to check if a file is in use?
  2. Easiest way to read from and write to files
  3. Nested using statements in C#
  4. How to change the timeout on a .NET WebClient object
  5. How to find the most recent file in a directory using .NET, and without looping?
  6. Best way to resolve file path too long exception
  7. Better way to check if a Path is a File or a Directory?
  8. C# – Get a list of files excluding those that are hidden
  9. Mirroring console output to a file
  10. How to get files in a relative path in C#
  11. How can I create a temp file with a specific extension with .NET?
  12. How to remove a single Attribute (e.g. ReadOnly) from a File?
  13. How to insert characters to a file using C#
  14. How do I get the directory from a file’s full path?
  15. Check if an executable exists in the Windows path
  16. Read random line from a file? c#
  17. Getting files by creation date in .NET
  18. Delete files older than 3 months old in a directory using .NET
  19. Encrypt SQLite database in C#
  20. C# Searching for files and folders except in certain folders
  21. How costly is .NET reflection?
  22. Best way to compare two complex objects
  23. A generic list of anonymous class
  24. How to read a large (1 GB) txt file in .NET?
  25. .NET Memory issues loading ~40 images, memory not reclaimed, potentially due to LOH fragmentation
  26. How to convert a character in to equivalent System.Windows.Input.Key Enum value?
  27. Best way to update LINQ to SQL classes after database schema change
  28. Can’t await async extension method
  29. C# how to send email?
  30. .NET DateTime to SqlDateTime Conversion

Leave a Comment