Introduction to ASP.NET Download File
Download the file is one of the important key features for any of the web applications compare with any kind of programming language available in the market. ASP.net has some special objects so-called implicit objects, which have required responses and possible methods for a user to download the file features for any of the web applications. This feature is well known and very used for any kind of business requirements, like download or upload physical files, ensuring proper network trap, storing in server location sometime encrypted, ASP.net implicit object ensuring these critical features executing smart way with very less number of code.
Syntax:
ASP.net download file is mainly using for any web-based application where the requirement is similar to introducing upload and downloading utility as application features. Some common syntax normally used to introduce the same:
- Codebehind: Need to define the page name which should call in behind the page. Here developer needs to define the specific ASP.net object where the developer writes their specific code to download the file from client location to the server-side and keep it stored in a specific location.
- Inherits: Inheritance requires implementing downloading common features of ASP.net application. We need to specify the specific class name from which code-behind should take their logic. This is one of the mandatory parameters that need to pass if you specify codebehind in the page import.
- Asp:button: One of the key tags in ASP.net for declaring any specific button inside the page. Here we need to define the download button, which needs to be click for downloading as per file availability in the specific server define location.
- Asp:Label: The label needs to define where to return text needs to display on the screen. This text indicating download successfully or not, if somehow any error occurred in the processing, it will give error text in this box.
- Response: define response by providing attachment file name at the content-disposition field, give expected length in content-length, provide the required content type, then flush the response and transmitting the file.
Example to Implement ASP.NET Download File
Download file is one the key feature for any of the web applications in spite of any programming language we used. Normally developer decided to provide critical features of uploading and downloading documents from the web applications. Documents can be any type; it depends on business logic. As per the client requirements, all kinds of documents can be uploaded or downloaded from the screen. XLS spreadsheet, Word Document, PDF, or PPT anything can be downloaded from the application. It also makes sure to downloaded files that should be secure and does not tamper. For security purpose, some of the application maintain file signature, which normally ensuring the content of the file should not tamper and always be same whatever uploaded. This kind of feature is very much urgent in case validation of documents where those are very urgent and using for some extra facility. Also, this downloading done some network tap. So that document can tamper in-network travel as well, so some applications encrypted the file with some secure code, and then at the time of reading decrypt the same from the application and read it for further work. This one can give full security from hackers as well. If any file downloaded an entirely encrypted approach and maintained proper signature to ensure file content exactly the same whatever uploaded, then that application can be considered as a fully secure application, hackers have very little chance to tamper anything on that specific application.
As an example, we can create one specific ASP.net project, where downloading features integrated with proper output as expected.
- Create a New Project from the File option. File -> New -> Project
- Choose Visual C# as a type of project.
- Then consider the same as a Web application.
- Then need to provide the .Net framework, here we choose 3.5 as the .net framework.
- Then click ASP.net application, and give one specific project name. Here we have provided the project name as ‘FileDownloadExample’.
Select Visual C#->select Web -> select .Net Framework 3.5 -> click on ASP.Net Web Application -> Write Project Name as “FileDownloadExample”
- We need to write the below code for giving a user view where they can download the file by clicking one button. The below page gives the opportunity to end-user to click one button just below the link, which internally calls one codebehind class for doing actual download activity from ASP.net application.
Code:
<%@ Page Title="Home Page" Language="C#" AutoEventWireup="true"
CodeBehind="Default.aspx.cs" Inherits="FileDownloadExample._Default" %>
<form id="form1" runat="server">
<p>
Click the button to download a file</p>
<asp:Button ID="Button1" runat="server" OnClick="Button1_Click" Text="Download" />
<br />
<br />
<asp:Label ID="Label11" runat="server"></asp:Label>
</form>- We have to design our screen in the proper approach so that the user can able to click for downloading the document.
- Below auto-generated code came into the logic.
- Writing requires code after clicking on the download button click event. It is given the proper result of downloading the file.
Code:
String path1 = "D:/OwnTask/abc.xlsx";
FileInfo file1 = new FileInfo(path1);
Response Res;
If(file1.Exists){
Res.Clear();
Res.AddHeader("Content-Disposition", "attachment; filename="+file1);
Res.AddHeader("Content-Length", file1.Length.toString());
Res.ContentType = "application/vnd.ms-excel";
Res.Flush();
Res.TransmitFile(file1.FullName);
Res.End();
}else{
Label11.Text = "File is not available for downloading";
}- Adding class FileDownloadExample, where we added the above logic which helps us to download the file from one web application page in ASP.net.
- Choosing one start page is mandatory to start one application, here we choose default.aspx.
- Click Debug button and start debugging
- Run the project on the local server. below screen open on the browser.
- Click on the download button -> if the file does not exist in the certain path, below alert will appear.
- If the file exists, it will download just like the below screens.
Conclusion
Uploading and downloading functions play an important role in any of the web applications. By using the above example, we can easily download the file. In addition to this, we can also download the file from the server to the local machine. I hope after going through this article, you got knowledge about downloading a file using the asp.net framework.
Recommended Articles
This is a guide to ASP.NET Download File. Here we discuss the Introduction and how to download file works in asp.net along with examples and code implementation. You may also look at the following articles to learn more –
