DataRowComparer_1.cs :  » 2.6.4-mono-.net-core » System.Data » System » Data » C# / CSharp Open Source

//
// DataRowComparer_1.cs
//
// Author:
//   Atsushi Enomoto  <atsushi@ximian.com>
//
// Copyright (C) 2008 Novell, Inc. http://www.novell.com
//

//
// Permission is hereby granted, free of charge, to any person obtaining
// a copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to
// permit persons to whom the Software is furnished to do so, subject to
// the following conditions:
// 
// The above copyright notice and this permission notice shall be
// included in all copies or substantial portions of the Software.
// 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
//

using System;
using System.Collections.Generic;

namespace System.Data{
  public sealed class DataRowComparer<TRow> : IEqualityComparer<TRow> where TRow : DataRow
  {
    static readonly DataRowComparer<TRow> default_instance = new DataRowComparer<TRow> ();

    public static DataRowComparer<TRow> Default {
      get { return default_instance; }
    }

    private DataRowComparer ()
    {
    }

    // LAMESPEC: neither of the parameters throws ArgumentNullException if it's null
    public bool Equals (TRow leftRow, TRow rightRow)
    {
      if (object.ReferenceEquals (leftRow, rightRow))
        return true;

      if (leftRow == null || rightRow == null)
        return false;

      int columnCount = leftRow.Table.Columns.Count;
      if (columnCount != rightRow.Table.Columns.Count)
        return false;

      for (int i = 0; i < columnCount; i++)
        if (!ColumnsEqual (leftRow [i], rightRow [i]))
          return false;
      return true;
    }

    bool ColumnsEqual (object leftCol, object rightCol)
    {
      if (object.ReferenceEquals (leftCol, rightCol))
        return true;

      if (leftCol == null || rightCol == null)
        return false;

      ValueType vt = leftCol as ValueType;
      if (vt != null && vt.Equals (rightCol))
        return true;

      return leftCol.Equals (rightCol);
    }
    
    public int GetHashCode (TRow row)
    {
      if (row == null)
        throw new ArgumentNullException ("row");

      DataTable table = row.Table;
      if (table == null)
        throw new ArgumentException ("The source DataRow objects does not belong to a DataTable.");

      DataColumnCollection columns = table.Columns;
      int columnCount = columns.Count;
      if (columnCount == 0)
        return 0;

      int ret = 0;
      object o;
      for (int i = 0; i < columnCount; i++) {
        o = row [i];
        if (o == null)
          continue;

        ret ^= o.GetHashCode ();
      }
        
      return ret;
    }
  }
}