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asp.net - How to rename file when upload in FileUpload

Rename uploaded file
FileUpload is an asp.net web server control that allows users to upload a file to a web server from their local computer. FileUpload server control displays a text box and a browse button on the web browser to select a file to upload from the client's local machine.

FileUpload control does not automatically save the uploaded file to the web server. FileUpload SaveAs() method allows us to save the contents of a client-uploaded file to a web server hard disk in a specified path. Using the FileUpload control's HasFile property we can verify that the FileUpload control contains a file.

FileUpload control's FileName property gets the client-uploaded file name. FileUpload control's PostedFile property allows us to get the additional properties on the uploaded file such as FileName, ContentLength, ContentType, etc.

We can change the client-uploaded default file name by using FileUpload control's SaveAs method. SaveAs() method requires passing a parameter named filename. This parameter value is a string that specifies the full path of the location of the server on which to save the uploaded file. using this parameter we can pass a new file name instead client uploaded file name. In the next paragraph, we describe a few techniques to do it.

First, we specify a folder on the webserver to save the uploaded file. Next, we get the client-uploaded file's extension using Path.GetExtension(path) method. This method exists in the System.IO namespace. Now we call the FileUpload SaveAs() method and pass a newly generated file name to save the uploaded file.

We generate a new path using adding three strings. The first string is the server folder location to save the file, the second is a new file name without an extension instead client file name, and the third is the client-uploaded file's extension. This is a simple process to rename a file when saving an uploaded file to the web server.

The following example code demonstrates to us how can we rename the client-uploaded file when saving it in the web server.
FileUploadRename.aspx

<%@ Page Language="C#" %>
<%@ Import Namespace="System.IO" %>

<!DOCTYPE html>

<script runat="server">
    protected void Button1_Click(object sender, System.EventArgs e) {
        string uploadFolder = Request.PhysicalApplicationPath + "UploadFile\\";
        if (FileUpload1.HasFile)
        {
            string extension = Path.GetExtension(FileUpload1.PostedFile.FileName);
            FileUpload1.SaveAs(uploadFolder + "Test"+ extension);
            Label1.Text = "File uploaded successfully as: " + "Test"+ extension;
        }
        else
        {
            Label1.Text = "First select a file.";
        }
    }
</script>

<html xmlns="http://www.w3.org/1999/xhtml">
<head id="Head1" runat="server">
    <title>asp.net FileUpload example: how to rename file when upload (change file name when upload)</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <h2 style="color:Green">asp.net FileUpload example: File Rename</h2>
        <asp:Label 
             ID="Label1" 
             runat="server" 
             Font-Size="Large"
             ForeColor="OrangeRed"
             >
        </asp:Label>
        <br /><br />
        <asp:FileUpload 
             ID="FileUpload1" 
             runat="server" 
             BackColor="DeepPink" 
             ForeColor="AliceBlue" 
             />
        <asp:Button 
             ID="Button1" 
             runat="server" 
             Font-Bold="true" 
             ForeColor="DeepPink" 
             OnClick="Button1_Click"
             Text="Upload It"
             />   
    </div>
    </form>
</body>
</html>
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