AjaxControlToolkit.HtmlEditorExtender :Key cannot be null. Parameter name: key

Getting error:Key can not be null .parameter name:key
web config :
<configSections> <sectionGroup name="system.web"> <section name="sanitizer" requirePermission="false" type="AjaxControlToolkit.Sanitizer.ProviderSanitizerSection, AjaxControlToolkit"/> </sectionGroup> </configSections>
Source Error: 
Line 41: Me.TextBoxControlPlaceHolder.Controls.Add(myTextBox) Line 42: Me.TextBoxControlPlaceHolder.Controls.Add(validator) Line 43: Dim myHTMLExtender = New AjaxControlToolkit.HtmlEditorExtender Line 44: Line 45: myHTMLExtender.ID = ds.Tables(0).Rows(i).Item(0) & "_HTM" So ...