ASP.NET - error con control

buenos dias que tal, estoy intentando agregar un control de calendario


control
ASPxDateEdit


son controles devExpress version 8.1

cuando abro la pagina en el explorador me sale el siguiente error, adjunto imagenes,


Server Error in '/' Application.
--------------------------------------------------------------------------------

Compilation Error
Description: An error occurred during the compilation of a resource required to service this request. Please review the following specific error details and modify your source code appropriately.

Compiler Error Message: CS0012: The type 'DevExpress.Web.ASPxClasses.ASPxDataWebControl' is defined in an assembly that is not referenced. You must add a reference to assembly 'DevExpress.Web.v8.1, Version=8.1.1.0, Culture=neutral, PublicKeyToken=9b171c9fd64da1d1'.

Source Error:



Line 469:
Line 470: [System.Diagnostics.DebuggerNonUserCodeAttribute()]
Line 471: private global::DevExpress.Web.ASPxEditors.ASPxDateEdit @__BuildControlASPxDateEdit1() {
Line 472: global::DevExpress.Web.ASPxEditors.ASPxDateEdit @__ctrl;
Line 473:


Source File: c:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\Temporary ASP.NET Files\root\a93fbdc7\ed63a714\App_Web_frmnewshippingwindows.aspx.cdcab7d2.2emyrwck.0.cs Line: 471



Show Detailed Compiler Output: