用户控制中的Eval不起作用

Question

<uc1:UploadImageControl 
     ID="UploadImageControl1" 
     runat="server" 
     SaveButtonID="btnUpdate"
     DeleteImageAfterSave="true" 
     ImageDirectory="centers" 
     ImageFileName='<%#Eval("CENTER_ID") %>'
     MaxUploadSize="5000000" />

当我尝试阅读imageFileName时，它不会返回中心ImageFileName的ID始终为空。

UploadImageControl.cs

 protected void Page_Load(object sender, EventArgs e)
{
    if (ImageFileName !="" && ImageDirectory != null) // here the ImageFileName  is always => ""
    {
        RIEditor.ImageUrl = ImageDirectory + ImageFileName;
        RIEditor.Visible = true;
    }
    // Response.Write(ajaxPanel.UniqueID);
}