>>Try reading again.
>>"To generate INSERT, UPDATE, or DELETE statements, the SqlCommandBuilder uses the SelectCommand property to retrieve a required set of metadata automatically. If you change the SelectCommand after the metadata has been retrieved, such as after the first update, you should call the RefreshSchema method to update the metadata."
>
>I did read this line. However, it doesn't explain why will it use all columns to generate WHERE clause. What exactly does required metadata mean? Why it can not see that PK column I retrieve is a PK column?

Look at the ConflictOptions property (http://msdn.microsoft.com/en-us/library/system.data.common.dbcommandbuilder.conflictoption%28v=vs.110%29.aspx) and the options that that enumeration has (http://msdn.microsoft.com/en-us/library/system.data.conflictoption%28v=vs.110%29.aspx). You might also want to look at the SetAllValues property (http://msdn.microsoft.com/en-us/library/system.data.common.dbcommandbuilder.setallvalues%28v=vs.110%29.aspx).