Szerkesztés

Megosztás a következőn keresztül:

FileUpload.HasFile Property

  • Reference

Definition

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

Gets a value indicating whether the FileUpload control contains a file.

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

Property Value

Boolean

true if the FileUpload contains a file; otherwise, false.

Attributes
BrowsableAttribute

Examples

The following example demonstrates how to create a FileUpload control that performs error checking. Before 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 occurs 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="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>

Remarks

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 before 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.

Applies to

See also