File upload: how to call a function without using button? C#

Question

0.00/5 (No votes)

See more:

Is there any way to call a function directly after selecting a file in the FileUpload control? Can we do it without having to click a button?

The function I want to call immediately after selecting the file is FileSelected(). After that the function FileSelected() calls another function called CheckFileType().

I do want to use a button afterwards to save the file, but not for calling the function.

What I have tried:

private void FileSelected()
{
    if (FileUpload1.HasFile)
    {
        if (CheckFileType(FileUpload1.FileName))
        {
            String filePath = "Cert/" + FileUpload1.FileName;
            txtpath1.Text = filePath;
        }
        else
        {
            Label1.Visible = true;
            Label1.Text = "You can upload ony images or PDF files.";
        }
    }
}

private bool CheckFileType(string fileName)
{
    string ext = Path.GetExtension(fileName);
    switch (ext.ToLower())
    {
        case ".gif":
        case ".png":
        case ".jpg":
        case ".jpeg":
        case ".pdf":
            return true;
        default:
            return false;
    }

}

Posted 19-Feb-18 8:33am

Nashii Angella

Updated 19-Feb-18 8:39am

RickZeeland

v2

Add a Solution

Comments

j snooze 19-Feb-18 17:08pm

This might be more helpful.
https://www.w3schools.com/tags/att_input_accept.asp

Laxmidhar tatwa technologies 19-Feb-18 23:28pm

switch (ext.ToLower())
{
case ".gif":
case ".png":
case ".jpg":
case ".jpeg":
case ".pdf":
return true;
break;
default:
return false;
}

Laxmidhar tatwa technologies 19-Feb-18 23:28pm

after return true breake; should be there

1 solution

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

F-ES Sitecore · Answer 1 · 2018-02-19T22:30:00

You can use the onchange event of the fileupload control

JavaScript Fileupload Object : onchange Event handlers - w3resource[^]

It's not going to work for what you want to do though. The file you have selected can't be "remembered" between postbacks so if you click a button programatically, or do anything else to send the file to the server like submit the form, then your code will check the file extension but when the page returns the file control will be empty again and there is nothing you can do about that.

So if you want to check the file's extension before you upload you need to do it via javascript. You still need your server-code as well though as malicious people can bypass your javascript.

There are various of doing that if you google but here are some

Validate file upload with html5 file api – BinaryTides[^]

Check File Size & Extension Before Uploading Using jQuery | All PHP Tricks[^]