Web designer - Upload file error - maximum file size

Hi,

in the Web Designer tool I added the "Upload File" node, but when I set a maximum file size (for example 10)  I get the following error message:

Error code: CS1061; Error description: VI_Employee_EditMasterData.cs(641,28): 'VI.WebRuntime.WebControls.FileUploader' does not contain a definition for 'InputFile' and no extension method 'InputFile' accepting a first argument of type 'VI.WebRuntime.WebControls.FileUploader' could be found (are you missing a using directive or an assembly reference?) (CS1061); Node: ; Property: ; Module: VI_Employee_EditMasterData; Project name: VI_StandardWeb; Compiler: CSharp

If I put just a number (e.g. 10), am I using the right format?
Why I get the error message above?

Version 8.1.3

Thank you,

Roberto