I have a file download code in vb .net but when i try to download any file (.rar in this case) everything downloads properly but when i open the .rar file WinRAR shows "The archive is damaged!" but when i download the same file from IDM its perfect and no error in WinRAR, how can i fix this???

This could be done by to many lost packets, or the way you receive and write the downloaded bytes so it would help if you can post your code here so that we can see and help you out.

 Required Tools : BackgroundWorker1, SavefileDialog1  
 -------------------------------------------  
 Name Spaces : Imports System.Net  
 ---------------------------  

   Dim whereToSave As String  
   Delegate Sub ChangeTextsSafe(ByVal length As Long, ByVal position As Integer, ByVal percent As Integer, ByVal speed As Double)  
   Delegate Sub DownloadCompleteSafe(ByVal cancelled As Boolean)  

 ----------------------------  
  Public Sub DownloadComplete(ByVal cancelled As Boolean)  

     Me.txtFileName.Enabled = True  
     Me.btnDownload.Enabled = True  
     Me.btnCancel.Enabled = False  
     If cancelled Then  
       Me.Label4.Text = "Cancelled"  
       MessageBox.Show("Download aborted", "Aborted")  
     Else  
       Me.Label4.Text = "Successfully downloaded"  
       MessageBox.Show("Successfully downloaded!")  
     End If  

     Me.ProgressBar1.Value = 0  
     Me.Label5.Text = "Downloading: "  
     Me.Label6.Text = "Save to: "  
     Me.Label3.Text = "File size: "  
     Me.Label2.Text = "Download speed: "  
     Me.Label4.Text = ""  

   End Sub  
 ---------------------------  
 Public Sub ChangeTexts(ByVal length As Long, ByVal position As Integer, ByVal percent As Integer, ByVal speed As Double)  

     Me.Label3.Text = "File Size: " & Math.Round((length / 1024), 2) & " KB"  
     Me.Label5.Text = "Downloading: " & Me.txtFileName.Text  
     Me.Label4.Text = "Downloaded " & Math.Round((position / 1024), 2) & " KB of " & Math.Round((length / 1024), 2) & "KB (" & Me.ProgressBar1.Value & "%)"  

     If speed = -1 Then  
       Me.Label2.Text = "Speed: calculating..."  
     Else  
       Me.Label2.Text = "Speed: " & Math.Round((speed / 1024), 2) & " KB/s"  
     End If  
     Me.ProgressBar1.Value = percent  

   End Sub  
 --------------------------  
 Private Sub btnDownload_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnDownload.Click  

     If Me.txtFileName.Text <> "" AndAlso Me.txtFileName.Text.StartsWith("http://") Then  

       Me.SaveFileDialog1.FileName = Me.txtFileName.Text.Split("/"c)(Me.txtFileName.Text.Split("/"c).Length - 1)  

       If Me.SaveFileDialog1.ShowDialog = Windows.Forms.DialogResult.OK Then  
         Me.whereToSave = Me.SaveFileDialog1.FileName  
         Me.SaveFileDialog1.FileName = ""  
         Me.Label6.Text = "Save to: " & Me.whereToSave  
         Me.txtFileName.Enabled = False  
         Me.btnDownload.Enabled = False  
         Me.btnCancel.Enabled = True  
         Me.BackgroundWorker1.RunWorkerAsync()  
       End If  
     Else  
       MessageBox.Show("Please insert valid URL for download")  
     End If  

   End Sub  
 -----------------------------  
  Private Sub BackgroundWorker1_DoWork(ByVal sender As System.Object, ByVal e As System.ComponentModel.DoWorkEventArgs) Handles BackgroundWorker1.DoWork  


     Dim theResponse As HttpWebResponse  
     Dim theRequest As HttpWebRequest  
     Try  
       theRequest = WebRequest.Create(Me.txtFileName.Text)  
       theResponse = theRequest.GetResponse  
     Catch ex As Exception  

       MessageBox.Show("An error occurred while downloading file. Possibe causes:" & ControlChars.CrLf & _  
               "1) File doesn't exist" & ControlChars.CrLf & _  
               "2) Remote server error", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error)  

       Dim cancelDelegate As New DownloadCompleteSafe(AddressOf DownloadComplete)  
       Me.Invoke(cancelDelegate, True)  
       Exit Sub  
     End Try  

     Dim length As Long = theResponse.ContentLength  
     Dim safedelegate As New ChangeTextsSafe(AddressOf ChangeTexts)  
     Me.Invoke(safedelegate, length, 0, 0, 0)  
     Dim writeStream As New IO.FileStream(Me.whereToSave, IO.FileMode.Create)  
     Dim nRead As Integer  
     Dim speedtimer As New Stopwatch  
     Dim currentspeed As Double = -1  
     Dim readings As Integer = 0  

     Do  
       If BackgroundWorker1.CancellationPending Then  
         Exit Do  
       End If  
       speedtimer.Start()  
       Dim readBytes(4095) As Byte  
       Dim bytesread As Integer = theResponse.GetResponseStream.Read(readBytes, 0, 4096)  
       nRead += bytesread  
       Dim percent As Short = (nRead * 100) / length  
       Me.Invoke(safedelegate, length, nRead, percent, currentspeed)  
       If bytesread = 0 Then Exit Do  
       writeStream.Write(readBytes, 0, bytesread)  
       speedtimer.Stop()  
       readings += 1  
       If readings >= 5 Then  
         currentspeed = 20480 / (speedtimer.ElapsedMilliseconds / 1000)  
         speedtimer.Reset()  
         readings = 0  
       End If  
     Loop  


     theResponse.GetResponseStream.Close()  
     writeStream.Close()  

     If Me.BackgroundWorker1.CancellationPending Then  
       IO.File.Delete(Me.whereToSave)  
       Dim cancelDelegate As New DownloadCompleteSafe(AddressOf DownloadComplete)  
       Me.Invoke(cancelDelegate, True)  
       Exit Sub  
     End If  

     Dim completeDelegate As New DownloadCompleteSafe(AddressOf DownloadComplete)  
     Me.Invoke(completeDelegate, False)  

 End Sub  
 -------------------  
 Private Sub mainForm_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load  

     Me.Label4.Text = ""  

 End Sub  
 -----------------------  
 Private Sub btnCancel_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnCancel.Click  

     Me.BackgroundWorker1.CancelAsync()  

 End Sub 

WebClient.DownloadFile seem to be easy to work with, have a look at it.

stackoverflow.com/questions/4066082/download-file-in-vb-net-2010

The above is one URL address, it also have a very good example of how to use it.

Don't forget, if your question has been answered to mark it as solved.

have a suggestion

why you use
me.label1.text when you simply can use label1.text?
it will make you code faster and the screept look more cleaner

This question has already been answered. Start a new discussion instead.