FileUpload.HasFile Proprietà
Definizione
Importante
Alcune informazioni sono relative alla release non definitiva del prodotto, che potrebbe subire modifiche significative prima della release definitiva. Microsoft non riconosce alcuna garanzia, espressa o implicita, in merito alle informazioni qui fornite.
Ottiene un valore che indica se il controllo FileUpload contiene un file.
public:
property bool HasFile { bool get(); };[System.ComponentModel.Browsable(false)]
public bool HasFile { get; }[<System.ComponentModel.Browsable(false)>]
member this.HasFile : boolPublic ReadOnly Property HasFile As BooleanValore della proprietà
true se la classe FileUpload contiene un file; in caso contrario, false.
- Attributi
Esempio
Nell'esempio seguente viene illustrato come creare un controllo che esegue il FileUpload controllo degli errori. Prima di salvare il file, il HasFile metodo viene chiamato per verificare che il controllo contenga un file da caricare. Inoltre, il File.Exists metodo viene chiamato per verificare se un file con lo stesso nome si verifica già nel percorso. In caso contrario, il nome del file da caricare viene preceduto da un carattere di sottolineatura prima che venga chiamato il SaveAs metodo. Ciò impedisce che il file esistente venga sovrascritto.
<%@ 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>
Commenti
La HasFile proprietà ottiene un valore che indica se il FileUpload controllo contiene un file da caricare. Usare questa proprietà per verificare che esista un file da caricare prima di eseguire operazioni nel file. Ad esempio, prima di chiamare il metodo per salvare il SaveAs file su disco, usare la HasFile proprietà per verificare che il file esista. Se HasFile restituisce true, chiamare il SaveAs metodo . Se restituisce false, visualizzare un messaggio all'utente che indica che il controllo non contiene un file.
