get directory of file c#

using System.IO;

string file = "C:\Documents\file.txt";
Path.GetDirectoryName(file);

string[] folders = System.IO.Directory.GetDirectories(@"C:\My Sample Path\","*", System.IO.SearchOption.AllDirectories);

 using (OpenFileDialog openFileDialog = new OpenFileDialog())
            {
                // TODO: Use LocalUser instead of Hardcode
                openFileDialog.InitialDirectory = @"C:\Users\username\Desktop"; 
                openFileDialog.Filter = "txt files (*.txt)|*.txt|All files (*.*)|*.*";
                openFileDialog.FilterIndex = 2;
                openFileDialog.RestoreDirectory = true;

                if (openFileDialog.ShowDialog() == DialogResult.OK)
                {
                    //Get the path of specified file
                    filePath = openFileDialog.FileName;

                    //Read the contents of the file into a stream
                    var fileStream = openFileDialog.OpenFile();

                    using (StreamReader reader = new StreamReader(fileStream))
                    {
                        fileContent = reader.ReadToEnd();
                    }
                }
            }