FileUpload.HasFile Propriedade
Definição
Importante
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Recebe um valor que indica se o controlo FileUpload contém um ficheiro.
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 BooleanValor de Propriedade
true se o FileUpload contiver um ficheiro; caso contrário, false.
- Atributos
Exemplos
O exemplo seguinte demonstra como criar um FileUpload controlo que realize verificação de erros. Antes de guardar o ficheiro, o HasFile método é chamado para verificar se o controlo contém um ficheiro para carregar. Além disso, o File.Exists método é chamado para verificar se já existe um ficheiro com o mesmo nome no caminho. Se o fizer, o nome do ficheiro a carregar é precedido por um sublinhado antes de o SaveAs método ser chamado. Isto impede que o ficheiro existente seja sobrescrito.
<%@ 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>
Observações
A HasFile propriedade recebe um valor que indica se o controlo FileUpload contém um ficheiro para carregar. Use esta propriedade para verificar se existe um ficheiro a carregar antes de realizar operações no ficheiro. Por exemplo, antes de chamar o SaveAs método para guardar o ficheiro no disco, use a HasFile propriedade para verificar se o ficheiro existe. Se HasFile regressar, truechama o SaveAs método. Se devolver false, exibe uma mensagem ao utilizador indicando que o controlo não contém um ficheiro.