>So is there a reason you didn't create a new table an manually loop through the rows? You are trying to force LINQ to do something it wasn't designed to do (create a new DataTable with a different structure). If you need the results as a DataTable, it needs to have a structure defined so that DataRows can be created for it. If you don't want to do that, you could write a method that would convert an IEnumberable< object> to a DataTable. Or you could create a class to hold the results of your query and use that instead of a DataTable to pass the results to the other function.

Here is an IEnumerable to DataTable extension method for anyone interested:

public static DataTable ToDataTable<T>(this IEnumerable<T> source) where T : class
{
	DataTable retVal = new DataTable();

	var props = typeof(T).GetProperties().ToList();

	retVal.Columns.AddRange(props.AsParallel()
		.Select(prop => new DataColumn(prop.Name, (Nullable.GetUnderlyingType(prop.PropertyType) ?? prop.PropertyType)))
		.ToArray());

	foreach (var obj in source)
	{
		var newRow = retVal.NewRow();
		foreach (var prop in props)
		{
			newRow.SetField(prop.Name, prop.GetValue(obj, null));
		}
		retVal.Rows.Add(newRow);
	}

	retVal.AcceptChanges();

	return retVal;
}