How do I create a directory on FTP server using C#?

Something like this:

// remoteUri points out an ftp address ("ftp://server/thefoldertocreate")
WebRequest request = WebRequest.Create(remoteUri);
request.Method = WebRequestMethods.Ftp.MakeDirectory;
WebResponse response = request.GetResponse();

(a bit late. how odd.)

Here is the answer if you want to create nested directories

There is no clean way to check if a folder exist on the ftp so you have to loop and create all the nested structure one folder at the time

public static void MakeFTPDir(string ftpAddress, string pathToCreate, string login, string password, byte[] fileContents, string ftpProxy = null)
    {
        FtpWebRequest reqFTP = null;
        Stream ftpStream = null;

        string[] subDirs = pathToCreate.Split('/');

        string currentDir = string.Format("ftp://{0}", ftpAddress);

        foreach (string subDir in subDirs)
        {
            try
            {
                currentDir = currentDir + "/" + subDir;
                reqFTP = (FtpWebRequest)FtpWebRequest.Create(currentDir);
                reqFTP.Method = WebRequestMethods.Ftp.MakeDirectory;
                reqFTP.UseBinary = true;
                reqFTP.Credentials = new NetworkCredential(login, password);
                FtpWebResponse response = (FtpWebResponse)reqFTP.GetResponse();
                ftpStream = response.GetResponseStream();
                ftpStream.Close();
                response.Close();
            }
            catch (Exception ex)
            {
                //directory already exist I know that is weak but there is no way to check if a folder exist on ftp...
            }
        }
    }

Use FtpWebRequest, with a method of WebRequestMethods.Ftp.MakeDirectory.

For example:

using System;
using System.Net;

class Test
{
    static void Main()
    {
        WebRequest request = WebRequest.Create("ftp://host.com/directory");
        request.Method = WebRequestMethods.Ftp.MakeDirectory;
        request.Credentials = new NetworkCredential("user", "pass");
        using (var resp = (FtpWebResponse) request.GetResponse())
        {
            Console.WriteLine(resp.StatusCode);
        }
    }
}