A system temporary folder or temporary directory is a directory used to hold temporary files. By default, when Ajax Uploader detects TempDirectory propery is not set, it will automatically use the system temporary folder. if web.config sepcified the TempDirectory appSetting, this would not take effects. You can turn this feature off by setting it to "false".

public bool AutoUseSystemTempFolder { get; set; }

Public Property AutoUseSystemTempFolder As Boolean
	Get
	Set

<asp:UploaderBase AutoUseSystemTempFolder="True|False" />