Configuring the Database Connectivity with the EntityCoreDataSource Component
This article explains how to specify the database connection used by the EntityCoreDataSource component so that the same DbContext works both at design time inside the report designer and at runtime in production.
Why a Separate Connection String Is Often Required
A typical EF Core DbContext reads its connection string from appsettings.json of the host application through IConfiguration. When the host is your own application, that file is loaded during report processing, and the DbContext works as expected. When the host is the Standalone Report Designer (.NET), the application's appsettings.json is not loaded, and the connection string is no longer available. When the host is the Web Report Designer, appsettings.json is available, but the component instantiates the DbContext through reflection rather than dependency injection — so a DbContext that relies solely on injected DbContextOptions will also fail to connect.
To overcome this, the EntityCoreDataSource component exposes a ConnectionString property. When configuring the data source in the Web Report Designer or the Standalone Report Designer, the wizard prompts for the connection string and stores it in the report definition. At processing time, the component forwards the value to the DbContext constructor that accepts a string argument at processing time. The DbContext must therefore expose such a constructor, as shown in the following Code First sample:
public class AppDbContext : DbContext
{
public AppDbContext()
{
}
public AppDbContext(string connectionString)
: base(BuildOptions(connectionString))
{
}
private static DbContextOptions<AppDbContext> BuildOptions(string connectionString)
{
return new DbContextOptionsBuilder<AppDbContext>()
.UseSqlServer(connectionString)
.Options;
}
}Setting the ConnectionString Property
To set the connection string in code, use either the property setter or the three-argument constructor:
var dataSource = new Telerik.Reporting.EntityCoreDataSource
{
Context = typeof(AppDbContext),
ContextMember = "People",
ConnectionString = "Server=.;Database=MSSQLLocalDB;Integrated Security=True;TrustServerCertificate=True"
};var dataSource = new Telerik.Reporting.EntityCoreDataSource(
"Server=.;Database=MSSQLLocalDB;Integrated Security=True;TrustServerCertificate=True",
typeof(AppDbContext),
"People");The wizard stores the value as an attribute on the EntityCoreDataSource element of the .trdp or .trdx definition. To centralize the value and avoid embedding credentials in the file, use a named connection instead. Store it in the configuration file of the report-hosting process and read it at startup before assigning it to the ConnectionString property.
Configuring the Designer Connection String
For the Report Designer Data Explorer and report preview to work in the desktop designers, store the design-time connection string with the report definition. For the Standalone Report Designer (.NET), this is typically a literal value set on the EntityCoreDataSource itself or a value loaded from the host application's appsettings.json. For the Web Report Designer, the connection string is read from the host service that exposes the Reporting REST Service.