Preliminary use of the FileUpload Control

Preliminary use of the FileUpload control:

1. Implement File Upload

Protected void btnSubmit_click (object sender, EventArgs e)

{

If (FileUpload1.HasFile = true)

{

String strErr = "";

// Obtain the size of the uploaded file

Int filesize = FileUpload1.PostedFile. ContentLength;

If (filesize> 1024*1024)

{

StrErr + = "the file size cannot exceed 1 MB \ n ";

}

If (strErr = "")

{

// Obtain the current path of the Server File

String path = Server. MapPath ("~ ");

// Save the uploaded file in the upload folder of the current path

FileUpload1.PostedFile. SaveAs (path + "\ upload \" + FileUpload1.FileName );

LblInfo. Text = "the file is saved successfully ";

}

}

Else

{

LblInfo. Text = "specify the file to be uploaded ";

}

}

 

2. restrict the types of uploaded files

// Get the file extension and convert it to lowercase
String fileExtension = System. IO. Path. GetExtension (FileUpload1.FileName). ToLower ();
// Only jpg and GIF images can be uploaded.
String [] allowExtension = {". jpg", ". gif", ". txt", ". xls "};
// Determine the type of the uploaded file www.2cto.com
For (int I = 0; I <allowExtension. Length; I ++)
{
If (fileExtension = allowExtension [I])
{
FileOk = true;
Break;
}
}

You can further use the FileUpload. PostedFile. ContentType attribute to determine the file type:
String fileContentType = FileUpload1.PostedFile. ContentType;
If (fileContentType = "image/bmp" | fileContentType = "image/gif" | fileContentType = "image/pjpeg ")
{

//-----
}

3. Name the uploaded file in time

String fileName = Server. MapPath ("~ ") +" \ Upload \ "+ DateTime. Now. ToString (" yyyyMMddHHmmss ") +". jpg ";

FileUpload1.SaveAs (fileName );

4. Upload large files

When using the FileUpload control in ASP. NET controls, you sometimes need to upload large files. By default, the maximum size of uploaded files is 4 MB. To upload a larger file, you can change two default settings in the configuration file: maxRequestLength and requestLengthDiskThreshold in httpRuntime. The former specifies the maximum size of the uploaded file, the latter sets the cache size, in KB.
For example:

<Configuration>
<System. web>
...
<HttpRuntime maxRequestLength = "10240" requestLengthDiskThreshold = "100"/>
...
</System. web>
</Configuration>

The preceding settings allow you to upload files up to 10 MB and change the cache threshold to kb.

However, if the setting is too large, a denial-of-service attack is caused by a large number of files being transferred to the server.

 

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