5 Responses to Advanced IComparer // Sorting on Multiple Values

1. Simon says:

   January 15, 2007 at 4:10 pm

   Here\’s a generic class I wrote which does the same sort of thing. You might find it useful in your 2.0 projects:

   public class AnythingComparer<T> : System.Collections.Generic.IComparer<T>{
   /// <summary>/// Sorts/Compares any type of object by any number of Properties/// </summary>/// <param name="property">Property name followed by sort direction. e.g. \’MyProperty DESC\'</param>
   public AnythingComparer(string property){   _properties = new string[] { property };}
   /// <summary>/// Sorts/Compares any type of object by any number of Properties/// </summary>/// <param name="properties">An array of property names followed and sort direction. e.g. {\’MyProperty DESC\’, \’Property2 ASC\’}</param>
   public AnythingComparer(string[] properties){  _properties = properties;}
   private string[] _properties;
   /// <summary>/// An array of property names followed and sort direction. e.g. {\’MyProperty DESC\’, \’Property2 ASC\’}/// </summary>public string[] Properties{  get { return _properties; }  set { _properties = value; }}
   public int Compare(T x, T y){  if (x.GetType() != y.GetType())    throw new ArgumentException("Can\’t compare " + x.GetType() + " with " + y.GetType());
     int res = 0;  for (int i = 0; i < _properties.Length; i++)  {      string[] args = _properties[i].Split(\’ \’);      string prop = args[0];      bool desc = args.Length > 0 && args[1].Equals("DESC", StringComparison.OrdinalIgnoreCase);      object o1 = x.GetType().GetProperty(prop).GetValue(x, null);      object o2 = y.GetType().GetProperty(prop).GetValue(y, null);      if (o1 == null)        throw new NullReferenceException();      if (o2 == null)        throw new NullReferenceException();
         IComparable comp1 = o1 as IComparable;      IComparable comp2 = o2 as IComparable;
         if (comp1 == null)        throw new ArgumentException("Property \’" + prop + "\’ of type " + o1.GetType() + " is not IComparable");      if (comp2 == null)        throw new ArgumentException("Property \’" + prop + "\’ of type " + o2.GetType() + " is not IComparable");      res = comp1.CompareTo(o2) * (desc ? -1 : 1);      if (res != 0)        return res;    }  return res;  }}
   … usage would be something like:
   List<SomeClass> ar = new List<SomeClass>();… populate the array …AnythingComparer<SomeClass> comp = new AnythingComparer<SomeClass>(new string[] { "SomeProp ASC", "SomeBool DESC", "SomeDate ASC", "SomeEnum ASC" });ar.Sort(comp);

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2. dootndo2 says:

   October 18, 2007 at 12:36 am

   I wanted to let you know that the AnythingComparer is awesome and works very well.  We came across a small issue with property names in different cases (camel case vs upper case).  So I added a check for this and though that i\’d post it back.
    
   Imports SystemImports System.Collections.GenericImports System.Text
   <Serializable()> Public Class AnythingComparer(Of T) Implements IComparer(Of T)
    \’\’\’ <summary>  \’\’\’ Sorts/Compares any type of object by any number of Properties  \’\’\’ </summary>  \’\’\’ <param name="property">Property name followed by sort direction. e.g. \’MyProperty DESC\'</param>
    Public Sub New(ByVal [property] As String)  _properties = New String() {[property]} End Sub
    \’\’\’ <summary>  \’\’\’ Sorts/Compares any type of object by any number of Properties  \’\’\’ </summary>  \’\’\’ <param name="properties">An array of property names followed and sort direction. e.g. {\’MyProperty DESC\’, \’Property2 ASC\’}</param>
    Public Sub New(ByVal properties As String())  _properties = properties End Sub
    Private _properties As String()
    \’\’\’ <summary>  \’\’\’ An array of property names followed and sort direction. e.g. {\’MyProperty DESC\’, \’Property2 ASC\’}  \’\’\’ </summary>  Public Property Properties() As String()  Get   Return _properties  End Get  Set(ByVal value As String())   _properties = value  End Set End Property
    Public Function Compare(ByVal x As T, ByVal y As T) As Integer Implements System.Collections.Generic.IComparer(Of T).Compare  If Not x.GetType() Is y.GetType() Then   Throw New ArgumentException("Cannot compare " & x.GetType().ToString() & " with " & y.GetType().ToString())  End If
     Dim res As Integer = 0  For i As Integer = 0 To _properties.Length – 1   Dim args As String() = _properties(i).Split(" "c)   Dim prop As String = args(0)   Dim desc As Boolean = args.Length > 0 AndAlso args(1).Equals("DESC", StringComparison.OrdinalIgnoreCase)
      \’ Updated here
      \’ get all properties for x/y (should be the same for same object type)   Dim props As System.Reflection.PropertyInfo() = x.GetType().GetProperties()
      Dim j As Integer   For j = 0 To props.Length    If props(j).Name.ToLower() = args(0).ToLower() Then     prop = props(j).Name     Exit For    End If   Next
      \’ End Update
      Dim o1 As Object = x.[GetType]().GetProperty(prop).GetValue(x, Nothing)   Dim o2 As Object = y.[GetType]().GetProperty(prop).GetValue(y, Nothing)
      If o1 Is Nothing Then    Throw New NullReferenceException()   End If   If o2 Is Nothing Then    Throw New NullReferenceException()   End If
      Dim comp1 As IComparable = TryCast(o1, IComparable)   Dim comp2 As IComparable = TryCast(o2, IComparable)
      If comp1 Is Nothing Then    Throw New ArgumentException("Property \’" & prop & "\’ of type " & o1.GetType().ToString() & " is not IComparable")   End If   If comp2 Is Nothing Then    Throw New ArgumentException("Property \’" & prop & "\’ of type " & o2.GetType().ToString() & " is not IComparable")   End If
      res = comp1.CompareTo(o2) * (IIf(desc, -1, 1))
      If res <> 0 Then    Return res
      End If  Next  Return res End Function
   End Class
    
   It would be used the same way as noted above.
    
   Thanks again!

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   April 15, 2008 at 4:14 am

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4. David says:

   February 5, 2010 at 5:58 pm

   Excellent, thank you!!

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5. guy says:

   May 2, 2012 at 11:14 am

   Thank you very much

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