Check if a string is a valid Windows directory (folder) path

I actually disagree with SLaks. That solution did not work for me. Exception did not happen as expected. But this code worked for me:

if(System.IO.Directory.Exists(path))
{
    ...
}

Call Path.GetFullPath; it will throw exceptions if the path is invalid.

To disallow relative paths (such as Word), call Path.IsPathRooted.

Path.GetFullPath gives below exceptions only

ArgumentException path is a zero-length string, contains only white space, or contains one or more of the invalid characters defined in GetInvalidPathChars. -or- The system could not retrieve the absolute path.

SecurityException The caller does not have the required permissions.

ArgumentNullException path is null.

NotSupportedException path contains a colon (":") that is not part of a volume identifier (for example, "c:\").

PathTooLongException The specified path, file name, or both exceed the system-defined maximum length. For example, on Windows-based platforms, paths must be less than 248 characters, and file names must be less than 260 characters.

Alternate way is to use the following :

/// <summary>
/// Validate the Path. If path is relative append the path to the project directory by default.
/// </summary>
/// <param name="path">Path to validate</param>
/// <param name="RelativePath">Relative path</param>
/// <param name="Extension">If want to check for File Path</param>
/// <returns></returns>
private static bool ValidateDllPath(ref string path, string RelativePath = "", string Extension = "")
{
    // Check if it contains any Invalid Characters.
    if (path.IndexOfAny(Path.GetInvalidPathChars()) == -1)
    {
        try
        {
            // If path is relative take %IGXLROOT% as the base directory
            if (!Path.IsPathRooted(path))
            {
                if (string.IsNullOrEmpty(RelativePath))
                {
                    // Exceptions handled by Path.GetFullPath
                    // ArgumentException path is a zero-length string, contains only white space, or contains one or more of the invalid characters defined in GetInvalidPathChars. -or- The system could not retrieve the absolute path.
                    // 
                    // SecurityException The caller does not have the required permissions.
                    // 
                    // ArgumentNullException path is null.
                    // 
                    // NotSupportedException path contains a colon (":") that is not part of a volume identifier (for example, "c:\"). 
                    // PathTooLongException The specified path, file name, or both exceed the system-defined maximum length. For example, on Windows-based platforms, paths must be less than 248 characters, and file names must be less than 260 characters.

                    // RelativePath is not passed so we would take the project path 
                    path = Path.GetFullPath(RelativePath);

                }
                else
                {
                    // Make sure the path is relative to the RelativePath and not our project directory
                    path = Path.Combine(RelativePath, path);
                }
            }

            // Exceptions from FileInfo Constructor:
            //   System.ArgumentNullException:
            //     fileName is null.
            //
            //   System.Security.SecurityException:
            //     The caller does not have the required permission.
            //
            //   System.ArgumentException:
            //     The file name is empty, contains only white spaces, or contains invalid characters.
            //
            //   System.IO.PathTooLongException:
            //     The specified path, file name, or both exceed the system-defined maximum
            //     length. For example, on Windows-based platforms, paths must be less than
            //     248 characters, and file names must be less than 260 characters.
            //
            //   System.NotSupportedException:
            //     fileName contains a colon (:) in the middle of the string.
            FileInfo fileInfo = new FileInfo(path);

            // Exceptions using FileInfo.Length:
            //   System.IO.IOException:
            //     System.IO.FileSystemInfo.Refresh() cannot update the state of the file or
            //     directory.
            //
            //   System.IO.FileNotFoundException:
            //     The file does not exist.-or- The Length property is called for a directory.
            bool throwEx = fileInfo.Length == -1;

            // Exceptions using FileInfo.IsReadOnly:
            //   System.UnauthorizedAccessException:
            //     Access to fileName is denied.
            //     The file described by the current System.IO.FileInfo object is read-only.-or-
            //     This operation is not supported on the current platform.-or- The caller does
            //     not have the required permission.
            throwEx = fileInfo.IsReadOnly;

            if (!string.IsNullOrEmpty(Extension))
            {
                // Validate the Extension of the file.
                if (Path.GetExtension(path).Equals(Extension, StringComparison.InvariantCultureIgnoreCase))
                {
                    // Trim the Library Path
                    path = path.Trim();
                    return true;
                }
                else
                {
                    return false;
                }
            }
            else
            {
                return true;

            }
        }
        catch (ArgumentNullException)
        {
            //   System.ArgumentNullException:
            //     fileName is null.
        }
        catch (System.Security.SecurityException)
        {
            //   System.Security.SecurityException:
            //     The caller does not have the required permission.
        }
        catch (ArgumentException)
        {
            //   System.ArgumentException:
            //     The file name is empty, contains only white spaces, or contains invalid characters.
        }
        catch (UnauthorizedAccessException)
        {
            //   System.UnauthorizedAccessException:
            //     Access to fileName is denied.
        }
        catch (PathTooLongException)
        {
            //   System.IO.PathTooLongException:
            //     The specified path, file name, or both exceed the system-defined maximum
            //     length. For example, on Windows-based platforms, paths must be less than
            //     248 characters, and file names must be less than 260 characters.
        }
        catch (NotSupportedException)
        {
            //   System.NotSupportedException:
            //     fileName contains a colon (:) in the middle of the string.
        }
        catch (FileNotFoundException)
        {
            // System.FileNotFoundException
            //  The exception that is thrown when an attempt to access a file that does not
            //  exist on disk fails.
        }
        catch (IOException)
        {
            //   System.IO.IOException:
            //     An I/O error occurred while opening the file.
        }
        catch (Exception)
        {
            // Unknown Exception. Might be due to wrong case or nulll checks.
        }
    }
    else
    {
        // Path contains invalid characters
    }
    return false;
}