Remove duplicates from DataTable and custom IEqualityComparer<DataRow>

How have I to implement IEqualityComparer<DataRow> to remove duplicates rows from a DataTable with next structure:

ID primary key, col_1, col_2, col_3, col_4

The default comparer doesn't work because each row has it's own, unique primary key.

How to implement IEqualityComparer<DataRow> that will skip primary key and compare only data remained.

I have something like this:

pu开发者_Go百科blic class DataRowComparer : IEqualityComparer<DataRow>
{
 public bool Equals(DataRow x, DataRow y)
 {
  return
   x.ItemArray.Except(new object[] { x[x.Table.PrimaryKey[0].ColumnName] }) ==
   y.ItemArray.Except(new object[] { y[y.Table.PrimaryKey[0].ColumnName] });
 }

 public int GetHashCode(DataRow obj)
 {
  return obj.ToString().GetHashCode();
 }
}

and

public static DataTable RemoveDuplicates(this DataTable table)
{
  return
    (table.Rows.Count > 0) ?
  table.AsEnumerable().Distinct(new DataRowComparer()).CopyToDataTable() :
  table;
}

but it calls only GetHashCode() and doesn't call Equals()

That is the way Distinct works. Intenally it uses the GetHashCode method. You can write the GetHashCode to do what you need. Something like

public int GetHashCode(DataRow obj)
{
    var values = obj.ItemArray.Except(new object[] { obj[obj.Table.PrimaryKey[0].ColumnName] });
    int hash = 0;
    foreach (var value in values)
    {
        hash = (hash * 397) ^ value.GetHashCode();
    }
    return hash;
}

Since you know your data better you can probably come up with a better way to generate the hash.