We integrated a hi-performance ASP.NET upload component - Ajax uploader into Rich Text Editor. Ajax Uploader allows you to select and upload multiple files at once. It also supports client side validation of the file size/type before uploading.

Unlike standard ASP.NET HtmlInputFile control, AJAX Uploader does not read the entire uploaded file into memory. It streams the data into a temporary file while the data is received. For this reason, you must specify a temporary file location. You should ensure that the ASPNET user (NetworkService in Windows Server 2003) has read/write permission to this specified folder.

You can easily specify the temporary file location by adding an entry into web.config:

<configuration>  
    <appSettings>  
        <add key="RichTextEditorTempPath" value="~/rtetemp" />  
    </appSettings>       
    ....   
</configuration>  

In web farm environments, the Url that you specify must map to a central location, which is saved to by all servers in the farm. This can be done using a virtual directory that maps to a common shared folder on the network.

<configuration>  
    <appSettings>  
        <add key="RichTextEditorTempPath" value="\\shareserver\rtetemp" />  
    </appSettings>       
    ....   
</configuration>  

If there is no temporary file location specified in the web.config file, RichTextEditor will use the system's temp folder.