using System.ComponentModel;

public class NoteInfo : System.ComponentModel.IDataErrorInfo {
    //...
    //Stores error descriptions for the Day, Month, Year and NoteID properties
    Hashtable propertyErrors;
    //Stores an error description for the item
    string noteError;

    
    public NoteInfo(int _noteID, int _day, int _month, int _year) {
        //...
        //Set errors to empty strings
        propertyErrors = new Hashtable();
        propertyErrors.Add("Day", "");
        propertyErrors.Add("Month", "");
        propertyErrors.Add("Year", "");
        propertyErrors.Add("NoteID", "");
        noteError = "";
    }

    public int NoteID { /*...*/ }
    public int Day { /*...*/ }
    public int Month { /*...*/ }
    public int Year { /*...*/ }

    //Gets and sets an error for the current item
    internal string NoteError {
        get { return noteError; }
        set {
            if(noteError == value) return;
            noteError = value;
            OnNoteChanged();
        }
    }

    public void ClearErrors() {
        SetColumnError("Day", "");
        SetColumnError("Month", "");
        SetColumnError("Year", "");
        NoteError = "";
    }

    //Sets an error for an item's property
    public void SetColumnError(string elem, string error) {
        if(propertyErrors.ContainsKey(elem)) {
            if((string)propertyErrors[elem] == error) return;
            propertyErrors[elem] = error;
            OnNoteChanged();
        }
    }

    //Gets an error for an item's property
    public string GetColumnError(string elem) {
        if(propertyErrors.ContainsKey(elem))
            return (string)propertyErrors[elem];
        else
            return "";
    }

    //The owner collection
    internal ProjectNotes Owner { /*...*/ }

    //Notify the owner collection about record changing
    protected void OnNoteChanged() {            
        if(Owner != null)
            Owner.OnRecordChanged(new ListChangedEventArgs(ListChangedType.ItemChanged, 
              Owner.IndexOf(this)));
    }


    #region IDataErrorInfo Members

    //Returns an error description set for the item's property
    string IDataErrorInfo.this[string columnName] {
        get {
            return GetColumnError(columnName);
        }
    }

    //Returns an error description set for the current item
    string IDataErrorInfo.Error {
        get { return noteError; }
    }

    #endregion
}

Imports System.ComponentModel

Public Class NoteInfo
    Implements System.ComponentModel.IDataErrorInfo

    '...
    'Stores error descriptions for the Day, Month, Year and NoteID properties
    Dim propertyErrors As Hashtable
    'Stores an error description for the item
    Dim _noteError As String


    Public Sub New(ByVal _noteID As Integer, ByVal _day As Integer, _
    ByVal _month As Integer, ByVal _year As Integer)
        '...
        'Set errors to empty strings
        propertyErrors = New Hashtable()
        propertyErrors.Add("Day", "")
        propertyErrors.Add("Month", "")
        propertyErrors.Add("Year", "")
        propertyErrors.Add("NoteID", "")
        _noteError = ""
    End Sub

    Public Property NoteID() As Integer
        '...
    End Property

    Public Property Day() As Integer
        '...
    End Property

    Public Property Month() As Integer
        '...
    End Property

    Public Property Year() As Integer
        '...
    End Property


    'Gets and sets an error for the current item
    Friend Property NoteError() As String
        Get
            Return _noteError
        End Get
        Set(ByVal Value As String)
            If _noteError = Value Then Return
            _noteError = Value
            OnNoteChanged()
        End Set
    End Property

    Public Sub ClearErrors()
        SetColumnError("Day", "")
        SetColumnError("Month", "")
        SetColumnError("Year", "")
        NoteError = ""
    End Sub

    'Sets an error for an item's property
    Public Sub SetColumnError(ByVal elem As String, ByVal _error As String)
        If propertyErrors.ContainsKey(elem) Then
            If CType(propertyErrors(elem), String) = _error Then Return
            propertyErrors(elem) = _error
            OnNoteChanged()
        End If
    End Sub

    'Gets an error for an item's property
    Public Function GetColumnError(ByVal elem As String) As String
        If propertyErrors.ContainsKey(elem) Then
            Return propertyErrors(elem)
        Else
            Return ""
        End If
    End Function

    'The owner collection
    Friend Property Owner() As ProjectNotes
        '...
    End Property

    'Notify the owner collection about record changing
    Protected Sub OnNoteChanged()
        If Not Owner Is Nothing Then Owner.OnRecordChanged(New ListChangedEventArgs(_
          ListChangedType.ItemChanged, Owner.IndexOf(Me)))
    End Sub

#Region " IDataErrorInfo Members "
    'Returns an error description set for the current item
    Friend ReadOnly Property [Error]() As String _
    Implements System.ComponentModel.IDataErrorInfo.Error
        Get
            Return NoteError
        End Get
    End Property

    'Returns an error description set for the item's property
    Default Public ReadOnly Property Item(ByVal columnName As String) As String _
    Implements System.ComponentModel.IDataErrorInfo.Item
        Get
            Return GetColumnError(columnName)
        End Get
    End Property
#EndRegion
End Class

public class ProjectNotes: CollectionBase, IBindingList {
    //...

    //Adds a new item to the collection
    public int Add(NoteInfo nInfo) {
        int index = List.Add(nInfo);            
        return index;
    }

    //Fires the IBindingList.ListChanged event.
    protected internal void OnRecordChanged(ListChangedEventArgs e) {
        if(ListChanged != null) ListChanged(this, e);
    }

    #region IBindingList Members
    // ...
    #endregion
}

Public Class ProjectNotes
    Inherits CollectionBase
    Implements IBindingList 
    '...

    'Adds a new item to the collection
    Public Function Add(ByVal nInfo As NoteInfo) As Integer
        Dim index As Integer = List.Add(nInfo)
        Return index
    End Function

    'Fires the IBindingList.ListChanged event
    Protected Friend Sub OnRecordChanged(ByVal e As ListChangedEventArgs)
        RaiseEvent ListChanged(Me, e)
    End Sub

#Region "IBindingList  Members "
    ' ...
#EndRegion
End Class

//Returns the name of the date property containing invalid data
private string IsValidDate(int day, int month, int year) {
    if(month < 1 || month > 12) return "Month";
    if(day < 1 || day > DateTime.DaysInMonth(year, month)) return "Day";
    if(year < 1980 || year > 2010) return "Year";
    return "";
}

private void ValidateData() {
    ProjectNotes notes = gridControl1.DataSource as ProjectNotes;
    foreach(NoteInfo nInfo in notes) {
        string valid = IsValidDate(nInfo.Day, nInfo.Month, nInfo.Year);
        nInfo.ClearErrors();
        if(valid != "") {
            nInfo.NoteError = "Check the date";
            nInfo.SetColumnError(valid, "Invalid " + valid);
        }    
    }
}

'Returns the name of the date property containing invalid data
private string IsValidDate(int day, int month, int year) {
    if(month < 1 || month > 12) return "Month";
    if(day < 1 || day > DateTime.DaysInMonth(year, month)) return "Day";
    if(year < 1980 || year > 2010) return "Year";
    return "";
}

private void ValidateData() {
    ProjectNotes notes = gridControl1.DataSource as ProjectNotes;
    foreach(NoteInfo nInfo in notes) {
        string valid = IsValidDate(nInfo.Day, nInfo.Month, nInfo.Year);
        nInfo.ClearErrors();
        if(valid != "") {
            nInfo.NoteError = "Check the date";
            nInfo.SetColumnError(valid, "Invalid " + valid);
        }    
    }
}