.NET Core web API + Dapper – Failure

It will break

With no error handling the code was a bit fragile so I modified the program.cs file and added support for the built in logging and Debug provider. To reduce the amount of code in the controller I have also moved the DTO to a separate file in the “models” folder.

namespace devMobile.WebAPIDapper.Lists
{
	public class Program
	{
		public static void Main(string[] args)
		{
			CreateHostBuilder(args).Build().Run();
		}

		public static IHostBuilder CreateHostBuilder(string[] args) =>
			 Host.CreateDefaultBuilder(args)
				.ConfigureLogging(logging =>
				{
					logging.ClearProviders();
					logging.AddDebug();
				})
				.ConfigureWebHostDefaults(webBuilder =>
				{
					webBuilder.UseStartup<Startup>();
				});
	}
}

To test the exception handling I “broke” the Dapper query embedded SQL.

namespace devMobile.WebAPIDapper.Lists.Controllers
{
	[Route("api/[controller]")]
	[ApiController]
	public class StockItemsFailureController: ControllerBase
	{
		private readonly string connectionString;
		private readonly ILogger<StockItemsFailureController> logger;

		public StockItemsFailureController(IConfiguration configuration, ILogger<StockItemsFailureController> logger)
		{
			this.connectionString = configuration.GetSection("ConnectionStrings").GetSection("WideWorldImportersDatabase").Value;

			this.logger = logger;
		}

		[HttpGet]
		public ActionResult<IEnumerable<Model.StockItemListDtoV1>> Get()
		{
			IEnumerable<Model.StockItemListDtoV1> response = null;

			try
			{
				using (SqlConnection db = new SqlConnection(this.connectionString))
				{
					response = db.Query<Model.StockItemListDtoV1>(sql: @"SELECTx [StockItemID] as ""ID"", [StockItemName] as ""Name"", [RecommendedRetailPrice], [TaxRate] FROM [Warehouse].[StockItems]", commandType: CommandType.Text);
				}
			}
			catch( SqlException ex)
			{
				logger.LogError(ex, "Retrieving list of StockItems");

				return this.StatusCode(StatusCodes.Status500InternalServerError);
			}

			return this.Ok(response);
		}
	}

The controller failed and the following error was displayed in the Visual Studio output window

devMobile.WebAPIDapper.Lists.Controllers.StockItemsFailureController: Error: Retrieving list of StockItems

System.Data.SqlClient.SqlException (0x80131904): Incorrect syntax near the keyword 'as'.
   at System.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean breakConnection, Action`1 wrapCloseInAction)
   at System.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean breakConnection, Action`1 wrapCloseInAction)
   at System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj, Boolean callerHasConnectionLock, Boolean asyncClose)
   at System.Data.SqlClient.TdsParser.TryRun(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj, Boolean& dataReady)
   at System.Data.SqlClient.SqlDataReader.TryConsumeMetaData()
   at System.Data.SqlClient.SqlDataReader.get_MetaData()
   at System.Data.SqlClient.SqlCommand.FinishExecuteReader(SqlDataReader ds, RunBehavior runBehavior, String resetOptionsString)
   at System.Data.SqlClient.SqlCommand.RunExecuteReaderTds(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, Boolean async, Int32 timeout, Task& task, Boolean asyncWrite, SqlDataReader ds)
   at System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, TaskCompletionSource`1 completion, Int32 timeout, Task& task, Boolean asyncWrite, String method)
   at System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method)
   at System.Data.SqlClient.SqlCommand.ExecuteReader(CommandBehavior behavior)
   at System.Data.SqlClient.SqlCommand.ExecuteDbDataReader(CommandBehavior behavior)
   at System.Data.Common.DbCommand.System.Data.IDbCommand.ExecuteReader(CommandBehavior behavior)
   at Dapper.SqlMapper.ExecuteReaderWithFlagsFallback(IDbCommand cmd, Boolean wasClosed, CommandBehavior behavior) in /_/Dapper/SqlMapper.cs:line 1055
   at Dapper.SqlMapper.QueryImpl[T](IDbConnection cnn, CommandDefinition command, Type effectiveType)+MoveNext() in /_/Dapper/SqlMapper.cs:line 1083
   at System.Collections.Generic.List`1..ctor(IEnumerable`1 collection)
   at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)
   at Dapper.SqlMapper.Query[T](IDbConnection cnn, String sql, Object param, IDbTransaction transaction, Boolean buffered, Nullable`1 commandTimeout, Nullable`1 commandType) in /_/Dapper/SqlMapper.cs:line 725
   at devMobile.WebAPIDapper.Lists.Controllers.StockItemsFailureController.Get() in C:\Users\BrynLewis\source\repos\WebAPIDapper\Lists\Controllers\03.StockItemsFailureController.cs:line 53
ClientConnectionId:f37eb089-a560-406d-8c24-cf904bb17d8a
Error Number:156,State:1,Class:15
The program '[16996] iisexpress.exe: Program Trace' has exited with code 0 (0x0).
The program '[16996] iisexpress.exe' has exited with code -1 (0xffffffff).

In a couple of future posts I will add support for Log4Net, nLog, Serilog and a couple other libraries.

NOTE : Error Handling approach has been updated

Enterprise Library V6 Data, Exception and Logging with Azure SDK 2.8

I have used the Enterprise library Blocks (which in different forms have been around since 2005) in quite a few projects. Individually the components are pretty good (not always best of breed) but they are well integrated and when used in the way which they were intended to be used work well.

I have just upgraded a client application to Visual Studio 2015 + .Net 4.5 + Enterprise Library V6 and some of the steps were not immediately obvious so hopefully this saves someone else some time. I have sample code for Azure Cloud Service Web and Worker roles.

For both web and worker roles I added the Azure Diagnostics listener to the listener config section of the enterprise library logging settings.

<loggingConfiguration name="" tracingEnabled="true" defaultCategory="General">
	<listeners>
    <add listenerDataType="Microsoft.Practices.EnterpriseLibrary.Logging.Configuration.SystemDiagnosticsTraceListenerData, Microsoft.Practices.EnterpriseLibrary.Logging, Version=6.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35&amp;amp;quot;
         type="Microsoft.WindowsAzure.Diagnostics.DiagnosticMonitorTraceListener, Microsoft.WindowsAzure.Diagnostics, Version=2.8.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35"
         name="AzureDiagnosticTraceListener"/>
   </listeners>
...
</loggingConfiguration>

I then enabled diagnostics on the role and configured the transfer of logs.

Azure Diagnostics configuration dialog

Azure Diagnostic Configuration

This replaces the DiagnosticMonitorConfiguration based approach

DiagnosticMonitorConfiguration diagConfig = DiagnosticMonitor.GetDefaultInitialConfiguration();
diagConfig.Logs.ScheduledTransferLogLevelFilter = LogLevel.Verbose;

// Enable scheduled transfer
diagConfig.Directories.ScheduledTransferPeriod = TimeSpan.FromMinutes(1);
diagConfig.Logs.ScheduledTransferPeriod = TimeSpan.FromMinutes(1);

...
DiagnosticMonitor.Start(&amp;amp;quot;Microsoft.WindowsAzure.Plugins.Diagnostics.ConnectionString&amp;amp;quot;, diagConfig);

For the web role I configured the exception and logging blocks in the Global.asax.cs file


protected void Application_Start()
{
   AreaRegistration.RegisterAllAreas();
   GlobalConfiguration.Configure(WebApiConfig.Register);
   FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
   RouteConfig.RegisterRoutes(RouteTable.Routes);
   BundleConfig.RegisterBundles(BundleTable.Bundles);

   // Load the Entlib logging block configuration
   LogWriterFactory logWriterFactory = new LogWriterFactory();
   LogWriter logWriter = logWriterFactory.Create();
   Logger.SetLogWriter(logWriter);

   // Load the Entlib Exception block configuration
   ExceptionPolicyFactory policyFactory = new ExceptionPolicyFactory();
   exManager = policyFactory.CreateManager();
}

For the worker role I configured the exception and logging blocks in the worker role startup

public override bool OnStart()
{
   // Set the maximum number of concurrent connections
   ServicePointManager.DefaultConnectionLimit = 12;
   ...
   LogWriterFactory logWriterFactory = new LogWriterFactory();
   LogWriter logWriter = logWriterFactory.Create();
   Logger.SetLogWriter(logWriter);
   ...
   return result;
}

Then in the webrole webapi2 API controllers you can use embedded SQL or call stored procedures with retries. (This sample code uses the Northwind database and default retry configuration)

public IEnumerable&amp;amp;lt;ProductDto&amp;amp;gt; Get()
{
var products = new List&amp;amp;lt;ProductDto&amp;amp;gt;();

WebApiApplication.exManager.Process(() =&amp;amp;gt;
{
Database db = new DatabaseProviderFactory().Create(&amp;amp;quot;NorthwindInstance&amp;amp;quot;);

RetryPolicy retry = new RetryPolicy&amp;amp;lt;SqlDatabaseTransientErrorDetectionStrategy&amp;amp;gt;(RetryStrategy.DefaultExponential);

var productAccessor = db.CreateSqlStringAccessor(
&amp;amp;quot;SELECT [ProductID],[ProductName],[QuantityPerUnit],[UnitPrice],[UnitsInStock],[Discontinued] FROM Products&amp;amp;quot;,
MapBuilder&amp;amp;lt;ProductDto&amp;amp;gt;
.MapAllProperties()
.Map(p =&amp;amp;gt; p.ID).ToColumn(&amp;amp;quot;ProductID&amp;amp;quot;)
.Map(p =&amp;amp;gt; p.Name).ToColumn(&amp;amp;quot;ProductName&amp;amp;quot;)
.Map(p =&amp;amp;gt; p.QuantityPerUnit).ToColumn(&amp;amp;quot;QuantityPerUnit&amp;amp;quot;)
.Map(p =&amp;amp;gt; p.UnitPrice).ToColumn(&amp;amp;quot;UnitPrice&amp;amp;quot;)
.Map(p =&amp;amp;gt; p.UnitsInStock).ToColumn(&amp;amp;quot;UnitsInStock&amp;amp;quot;)
.Map(p =&amp;amp;gt; p.Discontinued).ToColumn(&amp;amp;quot;Discontinued&amp;amp;quot;)
.Build());
products = retry.ExecuteAction(() =&amp;amp;gt;
{
return productAccessor.Execute().ToList();
});

}, &amp;amp;quot;ProductService&amp;amp;quot;);

return products;
}
public ProductDto Get(int id)
{
ProductDto productDto = null;

WebApiApplication.exManager.Process(() =&amp;amp;gt;
{
Database db = new DatabaseProviderFactory().Create(&amp;amp;quot;NorthwindInstance&amp;amp;quot;);

var productAccessor = db.CreateSqlStringAccessor(
&amp;amp;quot;SELECT [ProductID],[ProductName],[QuantityPerUnit],[UnitPrice],[UnitsInStock],[Discontinued] FROM Products WHERE [ProductID]=@ProductID&amp;amp;quot;,
new ProdductGetByProductIdParameterMapper(db),
MapBuilder&amp;amp;amp;lt;ProductDto&amp;amp;amp;gt;
.MapAllProperties()
.Map(p =&amp;amp;gt; p.ID).ToColumn(&amp;amp;quot;ProductID&amp;amp;quot;)
.Map(p =&amp;amp;gt; p.Name).ToColumn(&amp;amp;quot;ProductName&amp;amp;quot;)
.Map(p =&amp;amp;gt; p.QuantityPerUnit).ToColumn(&amp;amp;quot;QuantityPerUnit&amp;amp;quot;)
.Map(p =&amp;amp;gt; p.UnitPrice).ToColumn(&amp;amp;quot;UnitPrice&amp;amp;quot;)
.Map(p =&amp;amp;gt; p.UnitsInStock).ToColumn(&amp;amp;quot;UnitsInStock&amp;amp;quot;)
.Map(p =&amp;amp;gt; p.Discontinued).ToColumn(&amp;amp;quot;Discontinued&amp;amp;quot;)
.Build());

productDto = productAccessor.Execute(id).SingleOrDefault();

}, &amp;amp;quot;ProductService&amp;amp;quot;);

return productDto;
}