FileUpload.HasFile Eigenschaft

  • Referenz

Definition

Namespace:
System.Web.UI.WebControls
Assembly:
System.Web.dll

Ruft einen Wert ab, der angibt, ob das FileUpload-Steuerelement eine Datei enthält.

public:
 property bool HasFile { bool get(); };
[System.ComponentModel.Browsable(false)]
public bool HasFile { get; }
[<System.ComponentModel.Browsable(false)>]
member this.HasFile : bool
Public ReadOnly Property HasFile As Boolean

Eigenschaftswert

Boolean

true, wenn der FileUpload eine Datei enthält, andernfalls false.

Attribute
BrowsableAttribute

Beispiele

Im folgenden Beispiel wird veranschaulicht, wie Sie ein FileUpload Steuerelement erstellen, das eine Fehlerüberprüfung durchführt. Vor dem Speichern der Datei wird die HasFile -Methode aufgerufen, um zu überprüfen, ob das Steuerelement eine datei enthält, die hochgeladen werden soll. Darüber hinaus wird die File.Exists -Methode aufgerufen, um zu überprüfen, ob eine Datei mit demselben Namen bereits im Pfad vorkommt. Wenn dies der Fall ist, wird dem Namen der hochzuladenden Datei ein Unterstrich vorangestellt, bevor die SaveAs Methode aufgerufen wird. Dadurch wird verhindert, dass die vorhandene Datei überschrieben wird.

<%@ Page Language="C#" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head>
    <title>FileUpload.SaveAs Method Example</title>
<script runat="server">
        
    protected void  UploadButton_Click(object sender, EventArgs e)
    {
        // Before attempting to save the file, verify
        // that the FileUpload control contains a file.
        if (FileUpload1.HasFile) 
          // 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.";
    }
            
      void SaveFile(HttpPostedFile file)
      {            
        // Specify the path to save the uploaded file to.
        string savePath = "c:\\temp\\uploads\\";
            
        // Get the name of the file to upload.
        string fileName = FileUpload1.FileName;
            
        // Create the path and file name to check for duplicates.
        string pathToCheck = savePath + fileName;
        
        // Create a temporary file name to use for checking duplicates.
        string tempfileName = "";
            
        // Check to see if a file already exists with the
        // same name as the file to upload.        
        if (System.IO.File.Exists(pathToCheck)) 
        {
          int counter = 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 ++;
          }
          
          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.";
        }

        // 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);
            
      }
        
</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>

<%@ Page Language="VB" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head>
    <title>FileUpload.SaveAs Method Example</title>
<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>

Hinweise

Die HasFile -Eigenschaft ruft einen Wert ab, der angibt, ob das FileUpload Steuerelement eine datei enthält, die hochgeladen werden soll. Verwenden Sie diese Eigenschaft, um zu überprüfen, ob eine hochzuladende Datei vorhanden ist, bevor Sie Vorgänge für die Datei ausführen. Verwenden Sie beispielsweise vor dem Aufrufen der SaveAs Methode zum Speichern der Datei auf dem Datenträger die HasFile -Eigenschaft, um zu überprüfen, ob die Datei vorhanden ist. Wenn HasFile zurückgegeben wird true, rufen Sie die -Methode auf SaveAs . Wenn es zurückgibt false, wird dem Benutzer eine Meldung angezeigt, die angibt, dass das Steuerelement keine Datei enthält.

Gilt für:

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