Recursive queries

IQuery.Service can be used for issuing further recursive or subsequent queries from within the handler implementation.

public class Handler : IHandler<object, object>
{
    public void Handle(IQuery<object, object> query)
    {
        // Cast to string
        if (query.Request is not string str) return;
        // Parse to int32
        if (!Int32.TryParse(str, out int value)) return;

        // 
        ServiceRequest<CultureInfo> cultureInfoRequest = new ServiceRequest<CultureInfo>();
        // Recursive request
        CultureInfo? cultureInfo = query.Service.Get<ServiceRequest<CultureInfo>, CultureInfo>(cultureInfoRequest, query.CancellationToken, query.Context);
        // Cast to string
        query.Response.SetValue(value.ToString(cultureInfo));
    }
}

Note that, it is generally important to pass on query.CancellationToken and query.Context to subsequent queries. Though query.Context can be cloned and modified if needed.

// Recursive request
var result = query.Service.Get<ServiceRequest<CultureInfo>, CultureInfo>(cultureInfoRequest, query.CancellationToken, query.Context);

entry.LinkFromQuery<FurtherRequest, Response>(service, furtherRequest, cancellationToken) links result of further request to the entry.

// Further request
ServiceRequest<CultureInfo> cultureInfoRequest = new ServiceRequest<CultureInfo>();
// Link result to result of further query
query.Response.LinkFromQuery<ServiceRequest<CultureInfo>, object>(query.Service, cultureInfoRequest, query.CancellationToken);

Full Example

Full example

using System;
using System.Globalization;
using Avalanche.Service;

public class handler_recursion
{
    // <01>
    public class Handler : IHandler<object, object>
    {
        public void Handle(IQuery<object, object> query)
        {
            // Cast to string
            if (query.Request is not string str) return;
            // Parse to int32
            if (!Int32.TryParse(str, out int value)) return;

            // 
            ServiceRequest<CultureInfo> cultureInfoRequest = new ServiceRequest<CultureInfo>();
            // Recursive request
            CultureInfo? cultureInfo = query.Service.Get<ServiceRequest<CultureInfo>, CultureInfo>(cultureInfoRequest, query.CancellationToken, query.Context);
            // Cast to string
            query.Response.SetValue(value.ToString(cultureInfo));
        }
    }
    // </01>

    public class Handler2 : IHandler<object, object>
    {
        public void Handle(IQuery<object, object> query)
        {
            // Cast to string
            if (query.Request is not string str) return;
            // Parse to int32
            if (!Int32.TryParse(str, out int value)) return;

            // 
            ServiceRequest<CultureInfo> cultureInfoRequest = new ServiceRequest<CultureInfo>();
            // <02>
            // Recursive request
            var result = query.Service.Get<ServiceRequest<CultureInfo>, CultureInfo>(cultureInfoRequest, query.CancellationToken, query.Context);
            // </02>
            // Cast to string
            query.Response.SetValue(value.ToString(result));
        }
    }

    public class Handler3 : IHandler<object, object>
    {
        public void Handle(IQuery<object, object> query)
        {
            // <03>
            // Further request
            ServiceRequest<CultureInfo> cultureInfoRequest = new ServiceRequest<CultureInfo>();
            // Link result to result of further query
            query.Response.LinkFromQuery<ServiceRequest<CultureInfo>, object>(query.Service, cultureInfoRequest, query.CancellationToken);
            // </03>
        }
    }

}