Hosting the Telerik Reporting REST Service in an ASP.NET Core Application in .NET 6, .NET 8 and .NET 9 with Startup.cs

This article guides you on how to host a Reports Web Service in order to expose the Reports Generation Engine to an ASP.NET Core in .NET Web Application. The configuration of the application in this tutorial is set up in the Startup.cs file of the project.

If you prefer to use top level statements introduced with .NET 6, refer to the article Hosting in .NET 6+ with Top-Level Statements.

The guide is separated into sections for readability reasons. Along with the steps, it elaborates on the concepts and theory behind each step.

Prerequisites

Visual Studio 2019, version 16.8+ or higher
NET 6 SDK or higher

Using the REST Service Project Template

In Visual Studio open the Add New Project dialog and select Telerik Reporting REST Service project template. After clicking Create a menu pops up that allows you to configure the following properties of the REST Service: target framework, service clients (report viewer and report designer), Cross-Origin Resource Sharing, Host Application ID, and Application URL.

Set the Target Framework to .NET 6, .NET 8 or .NET 9.

Once you have configured the rest of the options to your liking, click Finish and a new project, containing all the necessary files and packages to host the Telerik Reporting REST service instance, will be added to your solution.

Manually configuring the Telerik Reporting REST Service

Creating a Sample ASP.NET Core in .NET Project

First, you need to create a new ASP.NET Core project:

Open Visual Studio 2019 or newer.
From the File menu, select New > Project.
In the Add a new Project dialog select ASP.NET Core Web Application project template. Choose a name and location for the project and click Next.
In the Create a new ASP.NET Core web application dialog select from the drop down .NET 6.0 (Long Term Support) , .NET 8 or .NET 9. Click on Create.

Add Report Definitions

In this tutorial, the resulting service will use the sample report definitions deployed with the Telerik Reporting product installer:

Find the sample reports in {Telerik Reporting installation path}\Report Designer\Examples.
Add a new folder to your solution called Reports and copy all sample reports into it.
Later in the tutorial we will make sure that the ReportsController is able to resolve the definitions for the requested reports from this project folder.

It is recommended to use declarative definitions (TRDP/TRDX/TRBP) authored using the Standalone Report Designer or the Web Report Designer in order to take advantage of their design-time tooling because the VS integrated report designer tooling is still not available in .NET projects.

Add the Required Dependencies

This guide applies the recommended NuGet package references approach to add the dependencies:

Reference the Telerik.Reporting.Services.AspNetCore (or Telerik.Reporting.Services.AspNetCore.Trial) package.
Optionally, to enable the Office OpenXML document formats (XLSX, DOCX, and PPTX) as export options, reference the Telerik.Reporting.OpenXmlRendering (or Telerik.Reporting.OpenXmlRendering.Trial) NuGet package.

The recommended way of adding the necessary dependencies is to use the Progress Telerik proprietary NuGet feed and reference the dependencies as NuGet packages. This would also add the indirect dependencies to your project bringing easier dependency management. Alternatively, the assemblies are available in the \Bin\net6.0\ and \Bin\netstandard2.0\ folders of the Telerik Reporting installation directory. However, this would require to manually add all indirect dependencies listed in .NET Support - Requirements section and also the following dependency package: Microsoft.AspNetCore.Mvc.NewtonsoftJson version 5.0.0 and DocumentFormat.OpenXML version 2.7.2.0 or above. Note that you need the last reference only to enable the Office OpenXML document formats. The Reporting engine relies on the GDI+ API which is available on the Windows OS. On Linux and macOS we use the SkiaSharp 2D Graphics Library based on Google's Skia Graphics Library.

Setup the Startup.cs file for the Reports service

When the Minimal API approach for hosting the Reporting REST Service is used, exceptions thrown by the service are propagated to and displayed in the Report Viewer. If this is undesired, set up the service using the 'Controllers' approach - Hosting the Reporting REST Service in ASP.NET Core with Controllers.

The ConfigureServices method inside the Startup.cs file in the project should be modified in order to enable the Reports Service functionality.

Call the AddNewtonsoftJson extension method on the IMvcBuilder object to enable the NewtonsoftJson serialization:
```
services.AddNewtonsoftJson();
```
Set up the ReportServiceConfiguration by invoking the AddTelerikReporting extension method on the IMvcBuilder object. In the code below, the first argument will represent the HostAppId of the ReportServiceConfiguration object, while the second is the path that will be passed to the UriReportSourceResolver:
```
var reportsPath = Path.Combine(builder.Environment.ContentRootPath, "Reports");

services.AddTelerikReporting("ReportingNet", reportsPath);
```
Register the Telerik Reporting Minimal API by invoking the UseTelerikReporting extension method on the WebApplication object. The application must also enable the endpoint routing middleware added by the UseRouting method:
```
app.UseTelerikReporting();
app.UseRouting();
```

Adding Connection Strings to the Configuration

The report generation engine can retrieve SQL Connection Strings and specific Report Generation Engine Settings that provide flexibility of the deployed application. It utilizes the IConfiguration interface for this purpose.

The .NET applications use a key-value JSON-based file named by default appSettings.json. The default ReportingEngineConfiguration will be initialized from appSettings.json or appsettings.{EnvironmentName}.json.

All Reporting-related configurations should be placed in the JSON configuraion file - (add one in the project root if such does not exist). For example, the ConnectionStrings setting should be configured in JSON-based format like this:

{
    "ConnectionStrings": {
        "Telerik.Reporting.Examples.CSharp.Properties.Settings.TelerikConnectionString": "Data Source=.\\SQLEXPRESS;Initial Catalog=AdventureWorks;Integrated Security=true"
    }
}

The above type of connection string lacks information about the data provider and will use System.Data.SqlClient as provider invariant name. When it's necessary to specify a different data provider, the following notation is also supported:

{
    "ConnectionStrings": {
        "Telerik.Reporting.Examples.CSharp.Properties.Settings.TelerikConnectionString": {
            "connectionString": "Data Source=.\\SQLEXPRESS;Initial Catalog=AdventureWorks;Integrated Security=true",
            "providerName": "System.Data.SqlClient"
        }
    }
}

The two types of connection string notations specified above can coexist in a single ConnectionStrings section.

The last supported type of ConnectionStrings configuration uses an array to provide information about each connection string:

{
    //...
    "ConnectionStrings": [
        {
            "name": "Telerik.Reporting.Examples.CSharp.Properties.Settings.TelerikConnectionString",
            "connectionString": "Data Source=.\\SQLEXPRESS;Initial Catalog=AdventureWorks;Integrated Security=true",
            "providerName": "System.Data.SqlClient"
        }
    ]
}

Test the service implementation

To ensure that the service operates, run the application and navigate to either of the General REST Service API URLs {applicationRoot}/api/reports/formats or {applicationRoot}/api/reports/version. The first should return a JSON representing the supported rendering extensions, and the second - the version of the Reporting REST Service.

You may need to enable Cross-Origin Resource Sharing (CORS), for example, if you use the REST Service from clients hosted in different domains.

Add the following code to the ConfigureServices method of the Startup.cs file to add a new CORS policy for the REST Service:

services.AddCors(corsOption => corsOption.AddPolicy(
    "ReportingRestPolicy",
    corsBuilder =>
    {
        corsBuilder.AllowAnyOrigin()
            .AllowAnyMethod()
            .AllowAnyHeader();
    }
));

Activate the above policy for the application by adding the next code in the Configure method of the Startup.cs file:

app.UseCors("ReportingRestPolicy");