check the link:
Sub UploadButton_Click(ByVal sender As Object, ByVal e As System.EventArgs)
' Before attempting to save the file, verify
' that the FileUpload control contains a file.
If (FileUpload1.HasFile) Then
' Call a helper method routine to save the file.
' Notify the user that a file was not uploaded.
UploadStatusLabel.Text = "You did not specify a file to upload."
Sub SaveFile(ByVal file As HttpPostedFile)
' Specify the path to save the uploaded file to.
Dim savePath As String = "c:\temp\uploads\"
' Get the name of the file to upload.
Dim fileName As String = FileUpload1.FileName
' Create the path and file name to check for duplicates.
Dim pathToCheck As String = savePath + fileName
' Create a temporary file name to use for checking duplicates.
Dim tempfileName As String
' Check to see if a file already exists with the
' same name as the file to upload.
If (System.IO.File.Exists(pathToCheck)) Then
Dim counter As Integer = 2
' If a file with this name already exists,
' prefix the filename with a number.
tempfileName = counter.ToString() + fileName
pathToCheck = savePath + tempfileName
counter = counter + 1
fileName = tempfileName
' Notify the user that the file name was changed.
UploadStatusLabel.Text = "A file with the same name already exists." + "
" + _
"Your file was saved as " + fileName
' Notify the user that the file was saved successfully.
UploadStatusLabel.Text = "Your file was uploaded successfully."
' Append the name of the file to upload to the path.
savePath += fileName
' Call the SaveAs method to save the uploaded
' file to the specified directory.