Exploiting the .NET Validation Frameworks: Listing 2.

Concatenating error messages into one string.

Default Public ReadOnly Property Item(columnName As String) 
  As String Implements System.ComponentModel.IDataErrorInfo.Item
  Get
    If _Errors.ContainsKey(columnName) Then
      Dim ErrorMessage As New Text.StringBuilder
      For Each ErrMsg As String In _Errors(columnName)
        ErrorMessage.Append(ErrMsg & "; ")
      Next
      Return ErrorMessage.ToString
    Else
      Return Nothing
    End If
  End Get
End Property

About the Author

Peter Vogel is a system architect and principal in PH&V Information Services. PH&V provides full-stack consulting from UX design through object modeling to database design. Peter tweets about his VSM columns with the hashtag #vogelarticles. His blog posts on user experience design can be found at http://blog.learningtree.com/tag/ui/.