ASP.NET Uploading Multiple Files using FileUpload control:
ASP.NET File upload control allows to upload multiple files at once. This feature is supported by all browsers which supports HTML5. File upload control has a property named “AllowMultiple” which accepts bool value of true or false, using which we can get all the files which are selected by the user on the front-end and save it on the server-side when submitting the form or a post back event. So let’s see how to make it work and get multiple files using File upload control in ASP.NET.
Example of uploading multiple files:
We will create two file upload control, one will accept only images and other will accept document like PDF, DOC.
Default.aspx:
<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="Default.aspx.cs" Inherits="AspTutorial.Default" %> <!DOCTYPE html> <html xmlns="http://www.w3.org/1999/xhtml"> <head runat="server"> <title>ASP.NET Multi-File upload</title> <style> </style> </head> <body style="font-family:Arial, Helvetica, sans-serif"> <form id="form1" runat="server"> <div> <h2>ASP.NET Multi file upload example:</h2> <br /> <h4>Image Upload:</h4> <asp:FileUpload runat="server" ID="imageUpload" AllowMultiple="true" accept="image/*"/> <asp:Button runat="server" ID="btnImageUpload" Text="Upload Images" OnClick="btnImageUpload_Click"/> <asp:Label runat="server" ID="lblImageNames" /> <br /> <h4>Document Upload:</h4> <asp:FileUpload runat="server" ID="documentUpload" AllowMultiple="true" accept=".pdf,.doc,.docx"/> <asp:Button runat="server" ID="btnDocumentUpload" Text="Upload Documents" OnClick="btnDocumentUpload_Click"/> <asp:Label runat="server" ID="lblDocumentNames" /> </div> </form> </body> </html>
Here, on both the labels, we will display a HTML link to navigate to the uploaded files by the users. Also we will rename all the files selected by the users and save it inside a folder called “UploadFiles“. Please create a folder with name “UploadFiles” in your project directory. 
Default.aspx.cs:
using System;
using System.Text;
using System.Web;
using System.Web.UI;
namespace AspTutorial
{
public partial class Default : Page
{
protected void Page_Load(object sender, EventArgs e)
{
}
protected void btnImageUpload_Click(object sender, EventArgs e)
{
try
{
StringBuilder files = new StringBuilder();
if(imageUpload.HasFiles)
{
foreach(HttpPostedFile file in imageUpload.PostedFiles)
{
string fileName = "image-"+ Guid.NewGuid() + DateTime.Now.ToString("ddMMyyyyHHmmss")+ System.IO.Path.GetExtension(file.FileName);
string filePath = System.IO.Path.Combine(Server.MapPath("~/UploadFiles/"), fileName);
file.SaveAs(filePath);
files.Append("<br/><a href='/UploadFiles/"+ fileName + "'>" + fileName + "</a>");
}
}
lblImageNames.Text = files.ToString() ;
}
catch(Exception ex)
{
lblDocumentNames.Text = ex.Message.ToString();
}
}
protected void btnDocumentUpload_Click(object sender, EventArgs e)
{
try
{
StringBuilder files = new StringBuilder();
if (documentUpload.HasFiles)
{
foreach (HttpPostedFile file in documentUpload.PostedFiles)
{
string fileName = "document-" + DateTime.Now.ToString("ddMMyyyyHHmmss") + System.IO.Path.GetExtension(file.FileName);
string filePath = System.IO.Path.Combine(Server.MapPath("~/UploadFiles/"), fileName);
file.SaveAs(filePath);
files.Append("<br/><a href='/UploadFiles/" + fileName + "'>" + fileName + "</a>");
}
}
lblDocumentNames.Text = files.ToString();
}
catch (Exception ex)
{
lblDocumentNames.Text = ex.Message.ToString();
}
}
}
}
All the files will be saved in the “UploadFiles” folder and we are using DateTime string with the file name to avoid duplicate file name issue.
