Conversion from DB Null value to string

I 'm calling this function below in a GridView but getting the error  Conversion from type 'DBNull' to type 'String' is not valid.   I thought I was handling this properly with the line sText.Equals(DBNull.Value) but it still errors out when the comments field is null in the database. Thanks 
<asp:TemplateField HeaderText="Comments"> <ItemTemplate> <%# FormatParagraph.FormatParagraphHTML(Eval("Comments"))%> </ItemTemplate> </asp:TemplateField> Public Shared Function FormatParagraphHTML(sText As String) As String Dim strReturn As String = String.Empty Try If sText = String.Empty OrElse sText.Equals(DBNull.Value) Then Return "" Else strReturn = Replace(sText, vbCrLf & vbCrLf, "<P>") strReturn = ...