Append is the same as the Add method, except that it does not return a value. Use Append when there is no need to know the index of the string after it has been added, or with descendants of TWideStrings for which the index returned is not meaningful.  

For example, the TWideStrings descendant used by memo objects uses an index to determine where to insert a string, but the inserted string does not necessarily end up as a single string in the list. Part of the inserted text may become part of the previous string, and part may be broken off into a subsequent string. The index returned by Add is not meaningful in this case. 

Add