ASP.NET

I want to upload larger file but getting error:


Network Error (tcp_error) 

A communication error occurred: ""
The Web Server may be down, too busy, or experiencing other problems preventing it from responding to requests. You may wish to try again at a later time.




    Sub UploadFile()

        Try
            Dim fileName As String = FulFile.PostedFile.FileName
            Dim requestFTP As WebRequest = WebRequest.Create("ftp:....................../" & fileName)
            requestFTP.Credentials = New NetworkCredential("User ID", "Password")
            requestFTP.Method = WebRequestMethods.Ftp.UploadFile

            Dim bufferLength As Integer = 2048
            Dim buffer As Byte() = New Byte(bufferLength - 1) {}

            Dim uploadStream As Stream = requestFTP.GetRequestStream()
            Dim contentLength As Integer = FulFile.PostedFile.InputStream.Read(buffer, 0, bufferLength)

            While contentLength <> 0
                uploadStream.Write(buffer, 0, contentLength)
                contentLength = FulFile.PostedFile.InputStream.Read(buffer, 0, bufferLength)
            End While
            FulFile.PostedFile.InputStream.Close()
            requestFTP = Nothing

            LblMsg.Text = "File Uploading Is SuccessFull..."

        Catch ep As Exception
            LblMsg.Text = ep.Message
        End Try

    End Sub

Hi,
I want to upload browsed file to the ftp server but getting this error


 Sub UploadFile()

        Try
            Dim fileName As String = FulFile.PostedFile.FileName
            Dim requestFTP As WebRequest = WebRequest.Create("ftp://...................." & fileName)
            requestFTP.Credentials = New NetworkCredential("userid", "password")
            requestFTP.Method = WebRequestMethods.Ftp.UploadFile


            Dim fStream As FileStream = FulFile.PostedFile.InputStream 'Error:Unable to cast object of type 'System.Web.HttpInputStream' to type 'System.IO.FileStream'.


            Dim bufferLength As Integer = 2048
            Dim buffer As Byte() = New Byte(bufferLength - 1) {}

            Dim uploadStream As Stream = requestFTP.GetRequestStream()
            Dim contentLength As Integer = fStream.Read(buffer, 0, bufferLength)

            While contentLength <> 0
                uploadStream.Write(buffer, 0, contentLength)
                contentLength = fStream.Read(buffer, 0, bufferLength)
            End While
            uploadStream.Close()
            fStream.Close()
            requestFTP = Nothing

            LblMsg.Text = "File Uploading Is SuccessFull..."

        Catch ep As Exception
            LblMsg.Text = ep.Message
        End Try

    End Sub

Could not load file or assembly 'AjaxControlToolkit' or one of its dependencies. This assembly is built by a runtime newer than the currently loaded runtime and cannot be loaded.
i am getting this error after uploaded my application on server. The same application works fine on local.i have used vs 2010,asp.net for the same