Questions about HTML form upload file

First of all, you can test the following piece of code

    <formID= "Form1"runat= "Server">        <inputtype= "File"name= "TTT" />        <inputtype= "Submit"value= "Tap" />    </form>

And then in the background

  var files= request.files;

You'll find there's nothing in files,

Why, the original is the form did not upload file, because a property in mischief Enctype

Because the form has a property Enctype property, enctype specifies how the form data should be encoded before being sent to the server.

By default, the form data is encoded as "application/x-www-form-urlencoded". That is, all characters are encoded before being sent to the server (spaces are converted to "+" plus signs, and special symbols are converted to ASCII HEX values).

value	Description
application/x-www-form-urlencoded	Encode all characters before sending (default)
Multipart/form-data	Character encoding is not. You must use this value when you use a form that contains a file upload control.
Text/plain	Spaces are converted to "+" plus signs, but special characters are not encoded.

From the above table enctype the value can be seen, the default will encode all characters, when there are files uploaded directly discarded.

It's time to replace

    <formID= "Form1"runat= "Server"enctype= "Multipart/form-data">        <inputtype= "File"name= "TTT" />        <inputtype= "Submit"value= "Tap" />    </form>

Can. Note that input file must have the name attribute, or it will not be uploaded.

Form uploading files for HTML