ajax tookit cobobox error rendering

Hello all

Any help appreciated

I am using vs2010, and ajaxcontroltoolkit15.1

I add combobox to page bu in design mode display error 

ajax tookit cobobox error

there was an error rendering the control

Parameter name stream value cannot be null

and in run time it does not work.

the code is

<cc1:ComboBox ID="ComboBox1" runat="server" AutoCompleteMode="Suggest" 
                    DataSourceID="sqdsField" DataTextField="FieldName" DataValueField="FieldSerial" 
                    MaxLength="0" style="display: inline;"></cc1:ComboBox>

Best regards