我如何使用watin为asp.net mvc上传控制上传文件

我正在写watin测试，我必须为mvc控件上传文件，但watin无法识别mvc上传控件。

这是银色代码：

<object type="application/x-silverlight-2" data="data:application/x-silverlight-2," id="ContentPlaceHolder1_ASPxUploadControl1_TextBox0_SLUploadHelper" width="70px" height="22px" style="position: absolute; background-color: transparent; top: -5000px; opacity: 0.01; left: 75px;" class=" ContentPlaceHolder1_ASPxUploadControl1_dxFITextBoxHover" title=""><param name="source" value="/DXR.axd?r=1_1-C5nV6"><param name="background" value="Transparent"><param name="windowless" value="true"><param name="minRuntimeVersion" value="3.0.40818.0"><param name="initParams" value="controlName=ContentPlaceHolder1_ASPxUploadControl1, inputIndex=0, multiselect=true, allowedMaxFileSize=4194304, allowedFileExtensions=.jpg;.jpeg;.jpe;.gif;.png, filter=*.jpg;*.jpeg;*.jpe;*.gif;*.png"><param name="onLoad" value="slOnLoad_ContentPlaceHolder1_ASPxUploadControl1_TextBox0_SLUploadHelper"><param name="onError" value="slOnError_ContentPlaceHolder1_ASPxUploadControl1_TextBox0_SLUploadHelper"></object>

问题是，silverlight上传控件是一个对象，watin不知道如何将其转换为FileUpload。我应该如何使用WatiN控制silverlight UploadFile。