Inject custom dependency in the ReportsController of a .NET Core application

Environment

Product	Progress® Telerik® Reporting
Project Type	ASP.NET Core

Description

ASP.NET Core provides built-in functionality for dependency injection. By default, the ReportsController, where the Telerik Reporting REST Service gets configured receives only an object of custom configuration class (e.g. ConfigurationService in our examples), where the IHostingEnvironment and IConfiguration are passed.
If you need to pass additional dependency, you may do it as explained below.

Solution

Let's demonstrate the approach with an example - how to provide a data source through inversion of control in the report dynamically. The Telerik Reporting uses System.Reflection to create instances of the custom objects at run-time. Therefore, they need public parameterless constructor in order to be successfully created. Hence, the ObjectDataSource cannot use a provider (e.g. ProductRepository) where a dependency (e.g. the database context) is injected, for example like :

public class ProductRepository : IProductRepository
{
    private readonly ApplicationDbContext context;

    public ProductRepository(ApplicationDbContext context)
    {
        this.context = context;
    }

    public IEnumerable<Product> GetProducts()
    {
        // return the data here, e.g.
        return this.context.Product.Take(20).ToList();
    }
}

In this case you may use Custom Resolver for resolving the TRDP reports and add the DataSource at run-time after instantiating the report. For the purpose it will be necessary to :

1) Implement a sample ConfigurationService class:

public class ConfigurationService
{
    public ConfigurationService(IHostingEnvironment environment)
    {
        this.Environment = environment;

        var configFileName = System.IO.Path.Combine(environment.ContentRootPath, "appsettings.json");
        var config = new ConfigurationBuilder()
                        .AddJsonFile(configFileName, true)
                        .Build();

        this.Configuration = config;
    }

    public IConfiguration Configuration { get; private set; }

    public IHostingEnvironment Environment { get; private set; }
}  

2) Change the ConfigureServices method of the Startup class to register ConfigurationService and IProductRepository, for example like :

public void ConfigureServices(IServiceCollection services)
{
    services.AddDbContext<...>(options => ...);
    ...
    services.AddScoped<IProductRepository, ProductRepository>();
    ... 
    // Configure dependencies for ReportServiceConfiguration.
    services.TryAddSingleton<ConfigurationService>(sp => new ConfigurationService(sp.GetService<IHostingEnvironment>()));
    services.TryAddScoped<IReportResolver, CustomReportResolver>();
    services.TryAddScoped<IReportServiceConfiguration>(sp =>
      new ReportServiceConfiguration
      {
        ReportingEngineConfiguration = sp.GetRequiredService<ConfigurationService>().Configuration,
        HostAppId = "Html5DemoAppCore",
        Storage = new FileStorage(),
        ReportResolver = sp.GetRequiredService<IReportResolver>()
      });
}

2) Pass a second parameter of IProductRepository in the constructor of ReportsController. Note that you can have only one constructor of the ReportsController (seems to be a limitation of the framework), hence you need to modify the existing constructor of the controller to receive the second parameter and pass it to the custom resolver :

public ReportsController(IReportServiceConfiguration reportServiceConfiguration, IProductRepository productRepository)
{
    ...
}

3) In the CustomReportResolver introduce a constructor that receives the repository and use the repository as required :

public class CustomReportResolver : IReportResolver
{
    ...
    private IProductRepository repository;

    public CustomReportResolver(IProductRepository repository)
    {
        this.repository = repository;
    }

    ReportSource IReportResolver.Resolve(string reportName)
    {
        // use **this.repository** as required in the Resolve method
        // For example the following code unpackages the TRDP report with name in 'reportName'
        // and sets the data source of 'table1' in its detail section 'detailSection1' to
        // the data returned by the GetProducts() method of the ProductRepository :

        var reportPackager = new ReportPackager();
        Report report = null;
        using (var sourceStream = System.IO.File.OpenRead(reportName))
        {
          report = (Report)reportPackager.UnpackageDocument(sourceStream);
        }

        DetailSection detail = (DetailSection)report.Items["detailSection1"];
        Table table = (Table)detail.Items["table1"];
        table.DataSource = this.repository.GetProducts();

        InstanceReportSource instanceReportSource = new InstanceReportSource();
        instanceReportSource.ReportDocument = report;

        return instanceReportSource;
     }
}