Hi I'm using Umbraco 7.5.11

I've been getting this error every so often which follows:

ERROR - Database exception occurred  System.InvalidOperationException: Internal connection fatal error.     at System.Data.SqlClient.TdsParser.TryRun(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj, Boolean& dataReady)     at System.Data.SqlClient.SqlDataReader.TryCloseInternal(Boolean closeReader)     at System.Data.SqlClient.SqlDataReader.Close()     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, String method, TaskCompletionSource`1 completion, Int32 timeout, Task& task, Boolean asyncWrite)     at System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method)     at System.Data.SqlClient.SqlCommand.ExecuteReader(CommandBehavior behavior, String method)     at System.Data.SqlClient.SqlCommand.ExecuteDbDataReader(CommandBehavior behavior)     at StackExchange.Profiling.Data.ProfiledDbCommand.ExecuteDbDataReader(CommandBehavior behavior) in c:\Code\github\SamSaffron\MiniProfiler\StackExchange.Profiling\Data\ProfiledDbCommand.cs:line 235     at System.Data.Common.DbCommand.System.Data.IDbCommand.ExecuteReader()     at Umbraco.Core.Persistence.PetaPocoCommandExtensions.<>c__DisplayClass4.<ExecuteReaderWithRetry>b__3()     at Umbraco.Core.Persistence.FaultHandling.RetryPolicy.ExecuteAction[TResult](Func`1 func)     at Umbraco.Core.Persistence.Database.<Query>d__7`1.MoveNext()

This seems to happen with only one specific method in the database, which follows:

        public ProductViewModel GetById(int id)
    {
        var productViewModel = new ProductViewModel();
        if (id <= 0) return productViewModel;

        using (var tr = _db.GetTransaction())
        {
            // Get the basic product information from the DB.
            var product = _db.SingleOrDefault<Product>("SELECT * FROM Products WHERE Id = @0", id);

            // Bind direct ProductViewModel's properties.
            productViewModel = Mapper.Map<ProductViewModel>(product);

            try
            {
                // Set the product's images
                productViewModel.Images = GetPicturesById(product.Id).ToList();

                // Set the Products Variants
                productViewModel.Variants = GetProductsVariantsByProductId(product.Id);

                // Set the Alternatives Products
                productViewModel.Alternatives = GetAlternativesProductsById(product.Id);

                // Set the Cross-sells Products
                productViewModel.CrossSells = GetCrossSellsProductsById(product.Id);

                // Set the Product SEO
                productViewModel.Seo = GetProductSeoById(product.Id);

                // Set the Size guide
                productViewModel.SizeGuide = _sizeGuidesRepository.GetById(product.SizeGuideTopicId);

                // Set the brand
                productViewModel.Brand = GetBrandById(productViewModel.Id);

                // Set the Market Sectors
                productViewModel.MarketSectorIds = GetMarketSectorsById(productViewModel.Id);

                // Set the Product Features
                productViewModel.ProductFeatures = GetProductFeaturesById(productViewModel.Id);

                // Set the Product News Ids
                productViewModel.RelatedNewsIds = GetProductNewsById(productViewModel.Id);

                tr.Complete();
            }
            catch (Exception e)
            {
                _log.Error(string.Format(@"Product Details - Id:{0}, Images:{1}, Variants:{2}, Alternatives:{3}, CrossSells:{4}, Seo:{5}, SizeGuide:{6}, Brand:{7}, Market Sectors:{8}, 
                                        Features:{9}, RelatedNewsIds:{10}. Product Object: {11}", productViewModel.Id, productViewModel.Images, productViewModel.Variants,
                                        productViewModel.Alternatives, productViewModel.CrossSells, productViewModel.Seo, productViewModel.SizeGuide, productViewModel.Brand,
                                        productViewModel.MarketSectorIds, productViewModel.ProductFeatures, productViewModel.RelatedNewsIds), e);
            }
        }

        return productViewModel;
    }

As you can see there's a lot of calls within the Using statement, however I'm unsure whether the Using statement is needed.

The method GetCrossSellsProductsById has a Using statement within it too (so effectively, a nested Using).

Each method within the Using statement use Database methods such as Fetch etc.

As previously mentioned, this error only occurs a couple of times per week, and only on a live database.

So my questions are:

1. Are Using statements required for basic database transactions?
2. Can nested Using statements cause trouble?

P.S. I know the code isn't very clean.