What is the purpose of .Services in the method: AddCustomHealthChecks and ConfigureServices ?

[santoshpatro]

I want to understand the purpose of ".Services" (present in the last line) as mentioned below :

@RehanSaeed : Can you please help me to know the purpose of the code in bold.

public static IServiceCollection AddCustomHealthChecks(this IServiceCollection services) =>
            services
                .AddHealthChecks()
                // Add health checks for external dependencies here. See https://github.com/Xabaril/AspNetCore.Diagnostics.HealthChecks
                .Services;

I also see in the below method:

public IServiceProvider ConfigureServices(IServiceCollection services) =>
            services
                .AddCorrelationIdFluent()
                .AddCustomCaching()
                .AddCustomOptions(this.configuration)
                .AddCustomRouting()
                .AddCustomResponseCompression()
                .AddCustomStrictTransportSecurity()
                .AddCustomHealthChecks()
                .AddHttpContextAccessor()
                .AddMvcCore()
                    .SetCompatibilityVersion(CompatibilityVersion.Version_2_2)
                    .AddAuthorization()
                    .AddJsonFormatters()
                    .AddCustomJsonOptions(this.hostingEnvironment)
                    .AddCustomCors()
                    .AddCustomMvcOptions(this.hostingEnvironment)
                .Services
                .AddCustomGraphQL(this.hostingEnvironment)
                .AddCustomGraphQLAuthorization()
                .AddProjectRepositories()
                .AddProjectSchemas()
                .BuildServiceProvider();

Any help on this is much appreciated ?

[VictorioBerra]

So you can keep chaining all those extension methods fluently. Without it you would just have to start a new line using the service collection from ConfigureServices.