What is the advantage of using Path.Combine over concatenating strings with '+'?

Question

I don\'t quite see the difference.

What could Path.Combine do better than perfectly working string concatenation?

I guess it\'s doing something

Answer 1

Path.Combine does more things than just a string concatenation. If you look at the source code;

• Checks both paths has invalid character or not
• Checks second parameter is root path or not
• Checks last character of first path is director or alt directory or volume separator or not. If not, concatenate both string with directory separator between then

Answer 2

Path.Combine uses the Path.PathSeparator and it checks whether the first path has already a separator at the end so it will not duplicate the separators. Additionally, it checks whether the path elements to combine have invalid chars.

Answer 3

According to this documentation Path.Combine internally performs a string concatenation using +-Operator.

 private 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;
    }

Answer 4

You avoid double path separators. If one path element already has a leading backslash. Path.Combine checks for that and ensures that only one backslash is present.

Answer 5

Here is the implementation

public static string Combine(string path1, string path2)
{
    if (path1 == null || path2 == null)
    {
        throw new ArgumentNullException((path1 == null) ? "path1" : "path2");
    }
    Path.CheckInvalidPathChars(path1, false);
    Path.CheckInvalidPathChars(path2, false);
    return Path.CombineNoChecks(path1, path2);
}

private static string CombineNoChecks(string path1, string path2)
{
    if (path2.Length == 0)
    {
        return path1;
    }
    if (path1.Length == 0)
    {
        return path2;
    }
    if (Path.IsPathRooted(path2))
    {
        return path2;
    }
    char c = path1[path1.Length - 1];
    if (c != Path.DirectorySeparatorChar && c != Path.AltDirectorySeparatorChar && c != Path.VolumeSeparatorChar)
    {
        return path1 + Path.DirectorySeparatorChar + path2;
    }
    return path1 + path2;
}