Added DBNull conversions where it makes sense and appended documentation.

Exposed DBNull extensions.

Author: Oren (electricessence)

Documentation.xml

@@ -498,13 +498,15 @@ public T[] ToArray<T>(Func<IDataRecord, T> transform)
 
 		/// <summary>
 		/// Iterates all records within the first result set using an IDataReader and returns the results.
+		/// DBNull values are left unchanged (retained).
 		/// </summary>
 		/// <returns>The QueryResult that contains all the results and the column mappings.</returns>
 		public QueryResult<Queue<object[]>> Retrieve()
 			=> Execute(command => command.Retrieve());
 
 		/// <summary>
 		/// Iterates all records within the current result set using an IDataReader and returns the desired results.
+		/// DBNull values are left unchanged (retained).
 		/// </summary>
 		/// <param name="ordinals">The ordinals to request from the reader for each record.</param>
 		/// <returns>The QueryResult that contains all the results and the column mappings.</returns>
@@ -513,6 +515,7 @@ public QueryResult<Queue<object[]>> Retrieve(IEnumerable<int> ordinals)
 
 		/// <summary>
 		/// Iterates all records within the current result set using an IDataReader and returns the desired results.
+		/// DBNull values are left unchanged (retained).
 		/// </summary>
 		/// <param name="n">The first ordinal to include in the request to the reader for each record.</param>
 		/// <param name="others">The remaining ordinals to request from the reader for each record.</param>
@@ -522,6 +525,7 @@ public QueryResult<Queue<object[]>> Retrieve(int n, params int[] others)
 
 		/// <summary>
 		/// Iterates all records within the first result set using an IDataReader and returns the desired results as a list of Dictionaries containing only the specified column values.
+		/// DBNull values are left unchanged (retained).
 		/// </summary>
 		/// <param name="columnNames">The column names to select.</param>
 		/// <returns>The QueryResult that contains all the results and the column mappings.</returns>
@@ -530,6 +534,7 @@ public QueryResult<Queue<object[]>> Retrieve(IEnumerable<string> columnNames)
 
 		/// <summary>
 		/// Iterates all records within the current result set using an IDataReader and returns the desired results.
+		/// DBNull values are left unchanged (retained).
 		/// </summary>
 		/// <param name="c">The first column name to include in the request to the reader for each record.</param>
 		/// <param name="others">The remaining column names to request from the reader for each record.</param>
@@ -560,15 +565,17 @@ public IEnumerable<T> Results<T>(IEnumerable<(string Field, string Column)> fiel
 			=> Execute(command => command.Results<T>(fieldMappingOverrides));
 
 		/// <summary>
-		/// Reads the first column from every record and returns the results as a list.
+		/// Reads the first column from every record and returns the results as a list..
+		/// DBNull values are converted to null.
 		/// </summary>
 		/// <returns>The list of transformed records.</returns>
-		public List<object> FirstOrdinalResults()
-			=> ToList(r => r.GetValue(0));
+		public IEnumerable<object> FirstOrdinalResults()
+			=> Execute(command => command.FirstOrdinalResults());
 
 
 		/// <summary>
-		/// Reads the first column from every record.
+		/// Reads the first column from every record..
+		/// DBNull values are converted to null.
 		/// </summary>
 		/// <returns>The enumerable of casted values.</returns>
 		public IEnumerable<T0> FirstOrdinalResults<T0>()

ExpressiveCommandBase.cs

@@ -175,7 +175,7 @@ public async Task<T> ExecuteScalarAsync<T>(Func<object, Task<T>> transform)
         /// <param name="token">An optional cancellation token.</param>
         /// <returns></returns>
         public Task IterateReaderAsync(Action<IDataRecord> handler, CancellationToken? token = null)
-            => ExecuteAsync(command => command.IterateReaderAsync(handler, token));
+            => ExecuteAsync(command => command.ForEachAsync(handler, token));
 
         /// <summary>
         /// Iterates asynchronously until the handler returns false.  Then cancels.
@@ -218,15 +218,16 @@ public Task<List<T>> TakeAsync<T>(Func<IDataRecord, T> transform, int count)
 
 
 		/// <summary>
-		/// Reads the first column from every record and returns the results as a list.
+		/// Reads the first column from every record and returns the results as a list..
+		/// DBNull values are converted to null.
 		/// </summary>
 		/// <returns>The list of transformed records.</returns>
-		public Task<List<object>> FirstOrdinalResultsAsync()
-			=> ToListAsync(r => r.GetValue(0));
-
+		public Task<IEnumerable<object>> FirstOrdinalResultsAsync()
+			=> ExecuteAsync(command => command.FirstOrdinalResultsAsync());
 
 		/// <summary>
-		/// Reads the first column from every record.
+		/// Reads the first column from every record..
+		/// DBNull values are converted to null.
 		/// </summary>
 		/// <returns>The enumerable of casted values.</returns>
 		public Task<IEnumerable<T0>> FirstOrdinalResultsAsync<T0>()