FileBytes Property
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FileUpload.FileBytes Property

 

Gets an array of the bytes in a file that is specified by using a FileUpload control.

Namespace:   System.Web.UI.WebControls
Assembly:  System.Web (in System.Web.dll)

<BindableAttribute(True)>
<BrowsableAttribute(False)>
Public ReadOnly Property FileBytes As Byte()

Property Value

Type: System.Byte()

A Byte array that contains the contents of the specified file.

Exception Condition
HttpException

The entire file was not read.

The FileUpload control does not automatically read the file from the client. You must explicitly provide a control or mechanism to allow the user to submit the specified file. For example, you can provide a button that the user can click to upload the file. The code that you write to save the specified file could call the FileBytes property, which returns the contents of the file.

Before calling the FileBytes property, you should use the HasFile property to verify that the FileUpload control contains a file to upload. If the HasFile returns true, call the FileBytes property. If it returns false, display a message to the user indicating that the control does not contain a file. If you do not provide error-handling code to verify that a file exists, an attempt to save a nonexistent file throws an HttpException exception.

The following example demonstrates how to create a FileUpload control. When the user clicks the Upload file button, the contents of the file are displayed as bytes in a text box on the page. This example uses the FileBytes property to upload the entire file.

<%@ 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.FileContent Property Example</title>
<script runat="server">

        Sub UploadButton_Click(ByVal sender As Object, ByVal e As System.EventArgs)
            ' Specify the path on the server to
            ' save the uploaded file to.
            Dim savePath As String = "c:\temp\uploads\"

            ' Before attempting to perform operations
            ' on the the file, verify that the FileUpload 
            ' control contains a file.
            If (FileUpload1.HasFile) Then

                ' Append the name of the file to upload to the path.
                savePath += FileUpload1.FileName

                ' Call the SaveAs method to save the 
                ' uploaded file to the specified path.
                ' This example does not perform all
                ' the necessary error checking.               
                ' If a file with the same name
                ' already exists in the specified path,  
                ' the uploaded file overwrites it.
                FileUpload1.SaveAs(savePath)

                ' Notify the user that the file was uploaded successfully.
                UploadStatusLabel.Text = "Your file was uploaded successfully."

                ' Call a helper routine to display the contents
                ' of the file to upload.
                DisplayFileContents(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 DisplayFileContents(ByVal file As HttpPostedFile)

            Dim fileLen As Integer
            Dim displayString As String = ""

            ' Get the length of the file.
            fileLen = FileUpload1.PostedFile.ContentLength

            ' Display the length of the file in a label.
            LengthLabel.Text = "The length of the file is " _
                               & fileLen.ToString() & " bytes."

            ' Create a byte array to hold the contents of the file.
            Dim Input(fileLen - 1) As Byte
            Input = FileUpload1.FileBytes

            ' Copy the byte array to a string.
            For loop1 As Integer = 0 To fileLen - 1
                displayString = displayString & Input(loop1).ToString()
            Next loop1

            ' Display the contents of the file in a 
            ' textbox on the page.
            ContentsLabel.Text = "The contents of the file as bytes:"

            Dim ContentsTextBox As New TextBox
            ContentsTextBox.TextMode = TextBoxMode.MultiLine
            ContentsTextBox.Height = Unit.Pixel(300)
            ContentsTextBox.Width = Unit.Pixel(400)
            ContentsTextBox.Text = displayString

            ' Add the textbox to the Controls collection
            ' of the Placeholder control.
            PlaceHolder1.Controls.Add(ContentsTextBox)

        End Sub

    </script>

</head>
<body>

    <h3>FileUpload.FileContent Property 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>

        <br /><br />

        <asp:Label id="UploadStatusLabel"
           runat="server">
        </asp:Label>  

        <hr />

        <asp:Label id="LengthLabel"
           runat="server">
        </asp:Label>  

        <br /><br />

        <asp:Label id="ContentsLabel"
           runat="server">
        </asp:Label>  

        <br /><br />

        <asp:PlaceHolder id="PlaceHolder1"
            runat="server">
        </asp:PlaceHolder>         

    </form>

</body>
</html>

.NET Framework
Available since 2.0
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