Check whether a path is valid

Question

Try Uri.IsWellFormedUriString():

• The string is not correctly escaped.

    http://www.example.com/path???/file name
  

• The string is an absolute Uri that represents an implicit file Uri.

    c:\\directory\filename
  

• The string is an absolute URI that is missing a slash before the path.

    file://c:/directory/filename
  

• The string contains unescaped backslashes even if they are treated as forward slashes.

    http:\\host/path/file
  

• The string represents a hierarchical absolute Uri and does not contain "://".

    www.example.com/path/file
  

• The parser for the Uri.Scheme indicates that the original string was not well-formed.

    The example depends on the scheme of the URI.
  

Or use the FileInfo as suggested in In C# check that filename is possibly valid (not that it exists).

I haven't had any problems with the code below. (Relative paths must start with '/' or '\').

private bool IsValidPath(string path, bool allowRelativePaths = false)
{
    bool isValid = true;

    try
    {
        string fullPath = Path.GetFullPath(path);

        if (allowRelativePaths)
        {
            isValid = Path.IsPathRooted(path);
        }
        else
        {
            string root = Path.GetPathRoot(path);
            isValid = string.IsNullOrEmpty(root.Trim(new char[] { '\\', '/' })) == false;
        }
    }
    catch(Exception ex)
    {
        isValid = false;
    }

    return isValid;
}

For example these would return false:

IsValidPath("C:/abc*d");
IsValidPath("C:/abc?d");
IsValidPath("C:/abc\"d");
IsValidPath("C:/abc<d");
IsValidPath("C:/abc>d");
IsValidPath("C:/abc|d");
IsValidPath("C:/abc:d");
IsValidPath("");
IsValidPath("./abc");
IsValidPath("./abc", true);
IsValidPath("/abc");
IsValidPath("abc");
IsValidPath("abc", true);

And these would return true:

IsValidPath(@"C:\\abc");
IsValidPath(@"F:\FILES\");
IsValidPath(@"C:\\abc.docx\\defg.docx");
IsValidPath(@"C:/abc/defg");
IsValidPath(@"C:\\\//\/\\/\\\/abc/\/\/\/\///\\\//\defg");
IsValidPath(@"C:/abc/def~`!@#$%^&()_-+={[}];',.g");
IsValidPath(@"C:\\\\\abc////////defg");
IsValidPath(@"/abc", true);
IsValidPath(@"\abc", true);

private bool IsValidPath(string path)
{
    Regex driveCheck = new Regex(@"^[a-zA-Z]:\\$");
    if (!driveCheck.IsMatch(path.Substring(0, 3))) return false;
    string strTheseAreInvalidFileNameChars = new string(Path.GetInvalidPathChars());
    strTheseAreInvalidFileNameChars += @":/?*" + "\"";
    Regex containsABadCharacter = new Regex("[" + Regex.Escape(strTheseAreInvalidFileNameChars) + "]");
    if (containsABadCharacter.IsMatch(path.Substring(3, path.Length - 3)))
        return false;

    DirectoryInfo dir = new DirectoryInfo(Path.GetFullPath(path));
    if (!dir.Exists)
        dir.Create();
    return true;
}

You can try this code:

try
{
  Path.GetDirectoryName(myPath);
}
catch
{
  // Path is not valid
}

I'm not sure it covers all the cases...

There are plenty of good solutions in here, but as none of then check if the path is rooted in an existing drive here's another one:

private bool IsValidPath(string path)
{
    // Check if the path is rooted in a driver
    if (path.Length < 3) return false;
    Regex driveCheck = new Regex(@"^[a-zA-Z]:\\$");
    if (!driveCheck.IsMatch(path.Substring(0, 3))) return false;

    // Check if such driver exists
    IEnumerable<string> allMachineDrivers = DriveInfo.GetDrives().Select(drive => drive.Name);
    if (!allMachineDrivers.Contains(path.Substring(0, 3))) return false;

    // Check if the rest of the path is valid
    string InvalidFileNameChars = new string(Path.GetInvalidPathChars());
    InvalidFileNameChars += @":/?*" + "\"";
    Regex containsABadCharacter = new Regex("[" + Regex.Escape(InvalidFileNameChars) + "]");
    if (containsABadCharacter.IsMatch(path.Substring(3, path.Length - 3)))
        return false;
    if (path[path.Length - 1] == '.') return false;

    return true;
}

This solution does not take relative paths into account.

The closest I have come is by trying to create it, and seeing if it succeeds.