Chapter 6. File Upload

Steps:

1. Write out the relative path position in the project first

String path = "Images/aaa.txt";

2. Map this relative path to absolute path

String endpath = Server.MapPath (path);

3. Save

Fileupload1.saveas ("Endpath");

Issue 1: file name is the same, easy to be overwritten

Method: Keep The original name of the file
String path = "images/" +fileupload1.filename;

Issue 2: file name is the same, multiple people upload the same file will be overwritten

Method: Name Add time splicing, user name splicing

String path= "images/" +datetime.now.tostring ("Yyyymmddhhmmss") +request.cookies["User". Value+fileupload1.filename;

Issue 3: Upload file format restrictions

Option 1:

Control properties: Accept = ". Jpg,.png,.jpeg";

Option 2:

Use JS to obtain the suffix name of the user's selected file and verify that it is consistent with the requirements

function
{        var fl = document.getElementById ("FileUpload1");         var aa = Fl.value.substr (fl.value.length-4, 4);         if (AA! = ". txt" && aa! = ". png" && AA! = ". jpg"
{            alert ("file format selection is incorrect!) ");             return false ;        }};

Question 4: file too large

Method 1, expansion

Web. config configuration file:
In kilobytes, default 4096, not too large because it consumes server memory

Method 2, File size limit
1. C # End Limit
if (FileUpload1.PostedFile.ContentLength > (4096 * 1024)) However, it is not useful

2. Client JS limit
Fl.files[0].size can get the size of the selected file, B is the unit

function () {        var fl = document.getElementById ("FileUpload1");         if (Fl.files[0].size > (1024x768 * 4)) {            alert ("file exceeds 4MB");             return false ;        }};

Chapter 6. File Upload