c#-webform-File Upload-fileupload control

//< upload > button    voidButton1_Click (Objectsender, EventArgs e) {        //determine if the file is selected        if(FileUpload1.FileName.Length <=0) {Label1.Text="no files are selected! "; return; }        //< upload > function code//------------------------------------------------------        //new folder uploads, setting save file name and type Abc.txt        stringPath ="Uploads/abc.txt"; //Map Absolute Path (Server.MapPath ())        stringEndpath = Server.MapPath (path);//Mapping Absolute Paths//Show upload Save folder absolute pathLabel1.Text =Endpath; //Save to Server (SaveAs ())Fileupload1.saveas (Endpath);//Save to Absolute path//------------------------------------------------------}

1, how to determine whether to select the file?
Fileupload.filename-
The file name of the selected file, if the length is not greater than 0, then no file is selected
Js-f.value.length

2, how to save to the server?
Fileupload.saveas ("absolute path");

3. How to get the absolute path? (Lee Brainstorming Lxc)
Write the relative path first-"Uploads/abc.txt"
Mapping relative paths to absolute paths-Server.MapPath ("Uploads/abc.txt");

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In the above method, only the. txt file can be uploaded, and the name can only be ABC. How do I keep the original name and file type?

// new Folder uploads, set save file name + selected file name

string path = "uploads/"+fileupload1.filename;

The same file will be overwritten. How do I keep the file's uniqueness from being overwritten?

Before file name + login Username + current time (accurate to milliseconds)

// new folder uploads, setting save file name        string " uploads/ " + request.cookies["username"]. Value + DateTime.Now.ToString ("yyyymmddhhmmssms") + fileupload1.filename;

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4, now can only be uploaded into TXT file, and the name can only be ABC
How do I keep a file's original name and file type?
"uploads/" + fileupload1.filename;

5, how to prevent the problem of duplicate name coverage?
"uploads/" + request.cookies["user"]. Value + DateTime.Now.ToString ("yyyymmddhhmmssms") + fileupload1.filename;

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How do I restrict the type of selected files? (Lee Brainstorming Lxc)

Front end FileUpload The type that is displayed when you select a file:

<asp:fileupload id="FileUpload1" runat="server" accept= " . Jpg,.png,.jpeg,.txt " />

The user can choose "All Files" publicly to select other types of files, how to limit?

JS Code:

<script type="Text/javascript">//< upload > button click events (JS priority highest)document.getElementById ("Button1"). onclick =function () {//Gets the selected file name        varfilename = document.getElementById ("FileUpload1"). Value; //4-bit or 5-bit after intercepting file name        varn = filename.substr (Filename.length-4,4); varm = Filename.substr (Filename.length-5,5); //determine if n or M does not meet the condition to terminate execution, otherwise continue        if(N!==". txt"&& N!==". jpg"&& N!==". PNG"&& m!==". JPEG") {alert ("Please choose the correct file format! "); return false; }    };</script>

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6. How to restrict the type of selected files?
Restrict ordinary people, add properties to the control-accept= ". Jpg,.png,.jpeg,.txt"
Limit the trouble:
document.getElementById ("Button1"). onclick = function () {
var fileName = document.getElementById ("FileUpload1"). Value;

var name = Filename.substr (filename.length-4, 4);
var name1 = Filename.substr (filename.length-5, 5);
if (name! = ". jpg" && name! = ". png" && name! = ". txt" && name1! = ". jpeg")
{
Alert ("Please select the correct file!") You're looking for something, huh? "); (Lee brainstorming Lxc)
return false;
}
};

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system default maximum upload size is 4M, if the file is too large to upload

How can I limit the size of my uploaded files? Expansion or limit size (Li brainstorming lxc)

Expansion:

In the Webconfig configuration file:

<configuration>  <system.web>    <compilation debug="false" targetframework="4.0" />    <!--set maximum upload file size 40M, Unit kb-->    "40960" />  </system.web></configuration>

Attention! Do not expand too much, or many people at the same time uploading large files will cause server memory shortage!

Limit size:

//< upload > button    voidButton1_Click (Objectsender, EventArgs e) {        //determine if the file is selected        if(FileUpload1.FileName.Length <=0) {Label1.Text="no files are selected! "; return; }        //determines if the length of the selected file is greater than 4M (the default is B)        if(FileUpload1.PostedFile.ContentLength >4*1024x768*1024x768) {Label1.Text="file length is too long!! "; return; }        //< upload > function code//------------------------------------------------------        //new folder uploads, setting save file name        stringPath ="uploads/"+ DateTime.Now.ToString ("yyyymmddhhmmssms") +Fileupload1.filename; //Map Absolute Path (Server.MapPath ())        stringEndpath = Server.MapPath (path);//Mapping Absolute Paths//Show upload Save folder absolute pathLabel1.Text =Endpath; //Save to Server (SaveAs ())Fileupload1.saveas (Endpath);//Save to Absolute path//------------------------------------------------------}

Disadvantage:< upload > Click, the System is first submitted to the background, and then judged, submitted to the background speed affected

JS End limit:

<script type="Text/javascript">//< upload > button click events (JS priority highest)document.getElementById ("Button1"). onclick =function () {//determine the length of the file to be uploaded        varf = document.getElementById ("FileUpload1"); if(f.files[0].size >4*1024x768*1024x768) {Label1.Text= Alert ("file length is too long!! "); return; }        //Gets the selected file name        varfilename = document.getElementById ("FileUpload1"). Value; //4-bit or 5-bit after intercepting file name        varn = filename.substr (Filename.length-4,4); varm = Filename.substr (Filename.length-5,5); //determine if n or M does not meet the condition to terminate execution, otherwise continue        if(N!==". txt"&& N!==". jpg"&& N!==". PNG"&& m!==". JPEG") {alert ("Please choose the correct file format! "); return false; }    };</script>

Advantage: The first judgment and then submit the upload, do not occupy the upload memory.

Note: C # side and JS end to write, in order to prevent bypass JS side directly upload

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7, control the size of the upload file
Expansion-system default allowed maximum upload length is 4MB
Webconfig in the configuration file
<system.web>
<compilation debug= "false" targetframework= "4.0"/>
</system.web>

Baidu Search, research, C # large file upload, breakpoint continued to pass.

Attention! Do not expand too much, or many people at the same time uploading large files will cause server memory shortage!

Limit size
C # End Limit:
if (fileupload1.postedfile.contentlength> (4*1024*1024))
{
Label1.Text = "File length too long!!!" ";
Return
}

JS End limit:
var f = document.getElementById ("FileUpload1");

if (F.files[0].size > (4 * 1024 * 1024)) {
Alert ("File Too big!!! ");
return false;
}

c#-webform-File Upload-fileupload control