Assembly: System.Web (in system.web.dll)
The HasFile property gets a value indicating whether the FileUpload control contains a file to upload. Use this property to verify that a file to upload exists prior to performing operations on the file. For example, before calling the SaveAs method to save the file to disk, use the HasFile property to verify that the file exists. If HasFile returns true, call the SaveAs method. If it returns false, display a message to the user indicating that the control does not contain a file.
The following code example demonstrates how to create a FileUpload control that performs error checking. Prior to saving the file, the HasFile method is called to verify that the control contains a file to upload. In addition, the File.Exists method is called to check whether a file with the same name already exists in the path. If it does, the name of the file to upload is prefixed with an underscore character before the SaveAs method is called. This prevents the existing file from being overwritten.
<%@ Page Language="VB" %> <html> <head> <script runat="server"> 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. SaveFile(FileUpload1.PostedFile) Else ' Notify the user that a file was not uploaded. UploadStatusLabel.Text = "You did not specify a file to upload." End If End Sub 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 While (System.IO.File.Exists(pathToCheck)) ' If a file with this name already exists, ' prefix the filename with a number. tempfileName = counter.ToString() + fileName pathToCheck = savePath + tempfileName counter = counter + 1 End While fileName = tempfileName ' Notify the user that the file name was changed. UploadStatusLabel.Text = "A file with the same name already exists." + "<br>" + _ "Your file was saved as " + fileName Else ' Notify the user that the file was saved successfully. UploadStatusLabel.Text = "Your file was uploaded successfully." End If ' 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. FileUpload1.SaveAs(savePath) End Sub </script> </head> <body> <h3>FileUpload.SaveAs Method Example</h3> <form ID="Form1" runat="server"> <h4>Select a file to upload:</h4> <asp:FileUpload id="FileUpload1" runat="server"> </asp:FileUpload> <br><br> <asp:Button id="UploadButton" Text="Upload file" OnClick="UploadButton_Click" runat="server"> </asp:Button> <hr /> <asp:Label id="UploadStatusLabel" runat="server"> </asp:Label> </form> </body> </html>
Windows 98, Windows 2000 SP4, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see System Requirements.