Thansk for your response. I changed the code to in the Thublist.ascx file as highlighted by you. But now I have started getting another error which says -

 

"FileInfo is a type in IO and can not be used as an expression". Here is code from my Thublist.ascx file

 

 <img border="0" src="<%# ThumbUrl((String)(DataBinder.Eval(Container.DataItem,"Name"))) %>" alt="<%# String_Name%>: <%# DataBinder.Eval(Container.DataItem, "Name")%>&#10;&#13;<%# String_Size%>: <%# (((System.IO.FileInfo)Container.DataItem).Length/1024).ToString("n0")%> KB&#10;&#13;<%# String_Createddate%>: <%# ((DataBinder.Eval(Container.DataItem, "CreationTime"))).ToShortDateString()%>&#10;&#13;<%# String_Modifieddate%>: <%# (DataBinder.Eval(Container.DataItem, "LastWriteTime")).ToShortDateString()%>" onmouseover="Check(this,1)" onmouseout="Check(this,0)" onclick="insert('<%# ImageUrl((String)(DataBinder.Eval(Container.DataItem,"Name"))) %>')" style="BORDER: white 1px solid" align="center">