Ошибка: не содержит статический метод Main() - C#

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO;
using System.Net;

namespace Client1Sharp
{
    
    public class Ftp{

            private string password;
            private string Host;
            private string userName; 
            private int bufferSize = 1024;
 
            public bool Passive = true;
            public bool Binary = true;
            public bool EnableSsl = false;
            public bool Hash = false;
 
            public Ftp(string Host, string userName, string password) {
                this.Host = Host;
                this.userName = userName;
                this.password = password;
            }
 
            public string ChangeWorkingDirectory(string path)
            {
                Host = combine(Host, path);
 
                return PrintWorkingDirectory();
            }
 
            public string DeleteFile(string fileName)
            {
                var request = createRequest(combine(Host, fileName), WebRequestMethods.Ftp.DeleteFile);
 
                return getStatusDescription(request);
            }
 
            public string DownloadFile(string source, string dest)
            {
                var request = createRequest(combine(Host, source), WebRequestMethods.Ftp.DownloadFile);
 
                byte[] buffer = new byte[bufferSize];
 
                using (var response = (FtpWebResponse)request.GetResponse())
                {
                    using (var stream = response.GetResponseStream())
                    {
                        using (var fs = new FileStream(dest, FileMode.OpenOrCreate))
                        {
                            int readCount = stream.Read(buffer, 0, bufferSize);
 
                            while (readCount > 0)
                            {
                                if (Hash)
                                    Console.Write("#");
 
                                fs.Write(buffer, 0, readCount);
                                readCount = stream.Read(buffer, 0, bufferSize);
                            }
                        }
                    }
 
                    return response.StatusDescription;
                }
            }
 
            public DateTime GetDateTimestamp(string fileName)
            {
                var request = createRequest(combine(Host, fileName), WebRequestMethods.Ftp.GetDateTimestamp);
 
                using (var response = (FtpWebResponse)request.GetResponse())
                {
                    return response.LastModified;
                }
            }
 
            public long GetFileSize(string fileName)
            {
                var request = createRequest(combine(Host, fileName), WebRequestMethods.Ftp.GetFileSize);
 
                using (var response = (FtpWebResponse)request.GetResponse())
                {
                    return response.ContentLength;
                }
            }
 
            public string[] ListDirectory()
            {
                var list = new List<string>();
 
                var request = createRequest(WebRequestMethods.Ftp.ListDirectory);
 
                using (var response = (FtpWebResponse)request.GetResponse())
                {
                    using (var stream = response.GetResponseStream())
                    {
                        using (var reader = new StreamReader(stream, true))
                        {
                            while (!reader.EndOfStream)
                            {
                                list.Add(reader.ReadLine());
                            }
                        }
                    }
                }
 
                return list.ToArray();
            }
 
            public string[] ListDirectoryDetails()
            {
                var list = new List<string>();
 
                var request = createRequest(WebRequestMethods.Ftp.ListDirectoryDetails);
 
                using (var response = (FtpWebResponse)request.GetResponse())
                {
                    using (var stream = response.GetResponseStream())
                    {
                        using (var reader = new StreamReader(stream, true))
                        {
                            while (!reader.EndOfStream)
                            {
                                list.Add(reader.ReadLine());
                            }
                        }
                    }
                }
 
                return list.ToArray();
            }
 
            public string MakeDirectory(string directoryName)
            {
                var request = createRequest(combine(Host, directoryName), WebRequestMethods.Ftp.MakeDirectory);
 
                return getStatusDescription(request);
            }
 
            public string PrintWorkingDirectory()
            {
                var request = createRequest(WebRequestMethods.Ftp.PrintWorkingDirectory);
 
                return getStatusDescription(request);
            }
 
            public string RemoveDirectory(string directoryName)
            {
                var request = createRequest(combine(Host, directoryName), WebRequestMethods.Ftp.RemoveDirectory);
 
                return getStatusDescription(request);
            }
 
            public string Rename(string currentName, string newName)
            {
                var request = createRequest(combine(Host, currentName), WebRequestMethods.Ftp.Rename);
 
                request.RenameTo = newName;
 
                return getStatusDescription(request);
            }
 
            public string UploadFile(string source, string destination)
            {
                var request = createRequest(combine(Host, destination), WebRequestMethods.Ftp.UploadFile);
 
                using (var stream = request.GetRequestStream())
                {
                    using (var fileStream = System.IO.File.Open(source, FileMode.Open))
                    {
                        int num;
 
                        byte[] buffer = new byte[bufferSize];
 
                        while ((num = fileStream.Read(buffer, 0, buffer.Length)) > 0)
                        {
                            if (Hash)
                                Console.Write("#");
 
                            stream.Write(buffer, 0, num);
                        }
                    }
                }
 
                return getStatusDescription(request);
            }
 
            public string UploadFileWithUniqueName(string source)
            {
                var request = createRequest(WebRequestMethods.Ftp.UploadFileWithUniqueName);
 
                using (var stream = request.GetRequestStream())
                {
                    using (var fileStream = System.IO.File.Open(source, FileMode.Open))
                    {
                        int num;
 
                        byte[] buffer = new byte[bufferSize];
 
                        while ((num = fileStream.Read(buffer, 0, buffer.Length)) > 0)
                        {
                            if (Hash)
                                Console.Write("#");
 
                            stream.Write(buffer, 0, num);
                        }
                    }
                }
 
                using (var response = (FtpWebResponse)request.GetResponse())
                {
                    return Path.GetFileName(response.ResponseUri.ToString());
                }
            }
 
            private FtpWebRequest createRequest(string method)
            {
                return createRequest(Host, method);
            }
 
            private FtpWebRequest createRequest(string uri, string method)
            {
                var r = (FtpWebRequest)WebRequest.Create(uri);
 
                r.Credentials = new NetworkCredential(userName, password);
                r.Method = method;
                r.UseBinary = Binary;
                r.EnableSsl = EnableSsl;
                r.UsePassive = Passive;
 
                return r;
            }
 
            private string getStatusDescription(FtpWebRequest request)
            {
                using (var response = (FtpWebResponse)request.GetResponse())
                {
                    return response.StatusDescription;
                }
            }
 
            private string combine(string path1, string path2)
            {
                return Path.Combine(path1, path2).Replace("", "/");
            }
            
        }
    }