resultsCombiner.cs

public void CombineResults(string groupCol, string targetCol, string differingCol)
	{
		var groupedResults = new Dictionary<string, IList<Dictionary<string, string>>>();

		foreach(var dbRow in QueryResults)
		{
			if (!groupedResults.ContainsKey(dbRow[groupCol]))
			{
				groupedResults.Add(dbRow[groupCol], new List<Dictionary<string, string>>());
			}

			groupedResults[dbRow[groupCol]].Add(dbRow);
		}

		var combinedResults = new List<Dictionary<string, string>>();

		foreach(var resultKey in groupedResults.Keys)
		{
			var results = groupedResults[resultKey];

			var combinedResult = new Dictionary<string, string>();
			
			foreach(var dbResult in results)
			{
				foreach(var key in dbResult.Keys)
				{
					if (!combinedResult.ContainsKey(key))
					{
						combinedResult.Add(key, dbResult[key]);
					}
					if(key == differingCol)
					{
						combinedResult.Add(dbResult[differingCol], dbResult[targetCol]);
					}
				}
			}

			combinedResults.Add(combinedResult);
		}
	}