Question

I have a DataSet with some DataTables that are linked together with DataRelations (classic order Header/Detail pair). Is there an easy way to denormalize the whole lot into a single DataTable with all the columns of the related tables?

The table names and columns are not known at compile time, and there may be more than two tables/relations.

Answer 1

Had the same problem my self, but since this question didn’t have an answer I had to write the denormalizer my self. Turned out it wasn’t all that difficult – so this is a first cut that you (or some one else who run into this problem) might be able to use/extend:

public class DataSetDenormalizer
{
    public void DenormalizeRelationships(DataSet dataSet)
    {
        IOrderedEnumerable<DataRelation> orderedRelationship = SortRelationshipsByNumberOfChildRows(dataSet);
        var tablesToRemove = new List<DataTable>();

        foreach (DataRelation relationship in orderedRelationship)
        {
            DenormalizeColumns(relationship);
            DenormalizeData(relationship);
            RemoveDenormalizedRelationships(dataSet, relationship, tablesToRemove);
        }
    }

    private IOrderedEnumerable<DataRelation> SortRelationshipsByNumberOfChildRows(DataSet dataSet)
    {
        var relationships = new List<DataRelation>();
        foreach (DataRelation relationship in dataSet.Relations)
            relationships.Add(relationship);
        return relationships.OrderBy(r => r.ChildTable.Rows.Count);
    }

    private void DenormalizeColumns(DataRelation relationship)
    {
        for (int columnIndex = 0; columnIndex < relationship.ParentTable.Columns.Count; ++columnIndex)
        {
            DataColumn column = relationship.ParentTable.Columns[columnIndex];
            if (relationship.ParentColumns.Contains(column)) continue;
            relationship.ChildTable.Columns.Add(new DataColumn(column.ColumnName, column.DataType));
        }
    }

    private void DenormalizeData(DataRelation relationship)
    {
        for (int rowIndex = 0; rowIndex < relationship.ChildTable.Rows.Count; ++rowIndex)
        {
            DataRow row = relationship.ChildTable.Rows[rowIndex];
            DataRow parentRow = row.GetParentRow(relationship);

            for (int columnIndex = 0; columnIndex < relationship.ParentTable.Columns.Count; ++columnIndex)
            {
                DataColumn column = relationship.ParentTable.Columns[columnIndex];
                if (relationship.ChildTable.Columns.Contains(column.ColumnName))
                {
                    row.SetField(column.ColumnName, parentRow[column]);
                }
            }
        }
    }

    private void RemoveDenormalizedRelationships(DataSet dataSet, DataRelation relationship, List<DataTable> tablesToRemove)
    {
        dataSet.Relations.Remove(relationship);
        relationship.ChildTable.Constraints.Remove(relationship.RelationName);

        if (!tablesToRemove.Contains(relationship.ParentTable))
            tablesToRemove.Add(relationship.ParentTable);

        int numberOfColumns = relationship.ChildColumns.Length;
        for (int columnIndex = 0; columnIndex < numberOfColumns; ++columnIndex)
        {
            relationship.ChildTable.Columns.Remove(relationship.ChildColumns[columnIndex]);
        }
    }
}