How can i upload only jpeg files?

Question

i want to upload files that are only jpeg, jpg etc. But i couldn't filter the files in the opening window. I want to change the text "all files" to jpeg etc. in the asp.net. (C#)

Solution 1

You could use a RegularExpressionValidator to validate if the user tries to upload jpeg-files or not:

<asp:FileUpload ID="FileUpload1" runat="server" /><br />
<br />
<asp:Button ID="Button1" runat="server" OnClick="Button1_Click" 
 Text="Upload File" />&nbsp;<br />
<br />
<asp:Label ID="Label1" runat="server"></asp:Label>
<asp:RegularExpressionValidator 
 id="RegularExpressionValidator1" runat="server" 
 ErrorMessage="Only jpeg files are allowed!" 
 ValidationExpression="^(([a-zA-Z]:)|(\\{2}\w+)\$?)(\\(\w[\w].*))
    +(.jpg|.JPG|.jpeg|.JPEG)$" 
 ControlToValidate="FileUpload1"></asp:RegularExpressionValidator>
<br />
<asp:RequiredFieldValidator 
 id="RequiredFieldValidator1" runat="server" 
 ErrorMessage="This is a required field!" 
 ControlToValidate="FileUpload1"></asp:RequiredFieldValidator>

on serverside:

    protected void Button1_Click(object sender, EventArgs e)
    {
        if (FileUpload1.HasFile)
        {
            string fileExt = 
               System.IO.Path.GetExtension(FileUpload1.FileName);

            if (fileExt == ".jpeg" || fileExt == ".jpg")
            {
                //do what you want with this file
            }
            else
            {
                Label1.Text = "Only .jpeg files allowed!";
            }
        }
        else
        {
            Label1.Text = "You have not specified a file.";
        }
    }

You should know that any user could change the extension f.e. from .exe to .jpg. The only way i know to check for the real file-type would be to use function from Urlmon.dll. Have a look at this SO-question if you want further informations: Using .NET, how can you find the mime type of a file based on the file signature not the extension

Solution 2

• How do I validate the file type of a file upload
• Check file extension of FileUpload control

Those will probably help you.

Comments

[mingos]

I believe it should be possible to check the uploaded files' mime type. It is possible with PHP, so it would be surprising it it wasn't possible with asp.net. As for HOW you can do that - sorry, I'm not the one to provide an answer :(.

[adrianbanks]

However you do the server side validation, you might want to also consider checking that the file actually contains a JPG (ie. it isn't just another file type with the .jpg extension).

[Brad Christie]

It's possible, just requires javascript/workaround. But Ultimately, you're right, you can't confirm it until after it's already been uploaded. And just to note, it's still a good idea to validate server-side to confirm the file's only an image (for malformed POST protection purposes)

[Viacheslav Smityukh]

You are right, you can check selected file, but you can't set files filter to the file select dialog.

[Brad Christie]

+1 for both server and client-side validation, in native ASP.

[Filip Ekberg]

You should rename those controls / methods. :)

[Tim Schmelter]

It's only an example, the OP didn't offer any markup, so i used this "anonymous" controls ;-)