StoredProcedure: added README

Author: gfraiteur

Framework/PostSharp.Samples.StoredProcedure/README.md

@@ -0,0 +1,24 @@
+
+This example implements something like P-Invoke, but it calls database stored procedures instead of native functions.
+
+Methods have to be defined as `extern` like this:
+
+```cs
+[MethodImpl(MethodImplOptions.InternalCall)]
+public extern IEnumerable<Speaker> GetActiveSpeakers();
+```
+
+In this design, methods must be instance (non-static) and declared in a class derived from `BaseDpApi`. This base class
+defined the `Connection` and `Transaction` properties used by the aspect.
+
+The `StoredProcedureAttribute` class is the implementation of the aspect itself. It is applied to the `BaseDbApi` class
+with inheritance and multicast enabled, so any `extern` method in a derived class will be turned into a stored 
+procedure call.
+
+The `MethodImpl` thing is ugly but unfortunately required. 
+
+To test this sample, you must create a SQL database, load `CreateDb.sql`, and change the connection string in `Program.Main`.
+
+This code is given for inspiration. A production-ready implementation should add error handling, test mappings,
+implement out parameters, and so on.
+

Framework/PostSharp.Samples.StoredProcedure/StoredProcedureAttribute.cs

@@ -95,6 +95,8 @@ public override void OnInvoke(MethodInterceptionArgs args)
         args.ReturnValue = this.mapDataReaderMethod.MakeGenericMethod(returnType.GetGenericArguments()[0]).Invoke(null, new object[] { reader, instance.Mapper });
       }
 
+      // TODO: Map out parameters back to method arguments.
+
     }
 
     public override async Task OnInvokeAsync(MethodInterceptionArgs args)
@@ -127,6 +129,8 @@ public override async Task OnInvokeAsync(MethodInterceptionArgs args)
 
       }
 
+      // TODO: Map out parameters back to method arguments.
+
     }
 
     private static IEnumerable<T> MapDataReader<T>(SqlDataReader reader, IMapper mapper)

README.md

@@ -24,6 +24,7 @@ or you can download them on [GitHub](https://www.github.com/postsharp/PostSharp.
 | [PostSharp.Samples.AutoDataContract](Framework/PostSharp.Samples.AutoDataContract/)                 | Automatically adds `[DataContract]` and `[DataMember]` attributes to derived classes and all properties | 
 | [PostSharp.Samples.Authorization](Framework/PostSharp.Samples.Authorization/)                       | Requires permissions before getting or setting fields or executing methods.                  | 
 | [PostSharp.Samples.NormalizeString](Framework/PostSharp.Samples.NormalizeString/)                   | Trims and lowercases strings before they are assigned to a field or property.
+| [PostSharp.Samples.StoredProcedure](Framework/PostSharp.Samples.StoredProcedure/)                   | Implements something like P-Invoke, but for database stored procedures.  |
 | **Diagnostics**                 
 | [PostSharp.Samples.Logging.Customization](Diagnostics/PostSharp.Samples.Logging.Customization/)     | Shows how to customize PostSharp Logging.                                                   | 
 | [PostSharp.Samples.Logging.Console](Diagnostics/PostSharp.Samples.Logging.Console/)                 | Demonstrates how to configure PostSharp Logging so that it directs its output to the *system console*.  |