JsonObjectCreationHandling.Populate is incompatible with reference handling occurs when System.Text.Json serialization options are misconfigured, often due to incompatible settings between ABP's distributed cache and the .NET JSON serializer. This typically happens after upgrading .NET or ABP versions, or when using distributed cache (e.g., Redis) with cached objects that have reference loops or require special handling.To resolve this in ABP 9.x:
Check Distributed Cache Configuration
JsonSerializerOptions, remove or update them to avoid setting both ReferenceHandler and JsonObjectCreationHandling.Populate.Clear Existing Cache
Update ABP and .NET Packages
Review Custom Serialization Code
AbpSystemTextJsonSerializer, ensure you do not set both ReferenceHandler and JsonObjectCreationHandling.Populate in your JsonSerializerOptions.Example: Correct Cache Serializer Configuration
Configure<AbpSystemTextJsonSerializerOptions>(options =>
{
options.JsonSerializerOptions.ReferenceHandler = null; // or ReferenceHandler.Preserve if needed, but not with Populate
// Do not set JsonObjectCreationHandling.Populate
});
For more details, see:
If the problem persists, ensure all microservices or app instances use the same ABP and .NET versions and cache configuration.
Sources:
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abp new Acme.BookStore -t microservice -u angular --database-provider postgresql
This template includes .NET 8, Angular, PostgreSQL, Redis, and Docker support.
docker-compose.yml for all services (API Gateway, IdentityServer, microservices, Angular UI, PostgreSQL, Redis). After generating the solution, check the /docker folder and root docker-compose.yml. You can run all services with:docker compose up --build
Make sure your docker-compose.yml exposes ports for API Gateway, IdentityServer, and Angular UI (e.g., 44300, 44301, 4200).
docker-compose.override.yml and each service’s Dockerfile. For PostgreSQL and Redis, use service names as hostnames (e.g., Host=postgres; for PostgreSQL, Configuration=redis:6379 for Redis). ABP microservice templates use environment variables like ConnectionStrings__Default and Redis__Configuration for configuration. Example:environment:
- ConnectionStrings__Default=Host=postgres;Port=5432;Database=abp;User Id=postgres;Password=yourpassword
- Redis__Configuration=redis:6379
All containers are on the same Docker network, so use service names (not localhost) for inter-service communication.
localhost:<exposed-port>..env files for secrets and environment-specific overrides.If you have issues accessing services on localhost, ensure ports are published in docker-compose.yml and not blocked by firewalls. For WSL2, Docker’s networking is compatible with localhost access.
Sources:
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dotnet ef migrations add for multiple DbContexts:8.0.8) is older than the runtime version (9.0.8).dotnet tool update --global dotnet-ef
Or, if you use a local tool manifest:
dotnet tool update dotnet-ef
DbContext of type WaveSecureVeltris.EntityFrameworkCore.ConfigDbContext.IDesignTimeDbContextFactory<ConfigDbContext>.ConfigDbContextFactory in your EntityFrameworkCore project. The factory should look like:public class ConfigDbContextFactory : IDesignTimeDbContextFactory<ConfigDbContext>
{
public ConfigDbContext CreateDbContext(string[] args)
{
var optionsBuilder = new DbContextOptionsBuilder<ConfigDbContext>();
optionsBuilder.UseSqlServer("Your_Connection_String_Here");
return new ConfigDbContext(optionsBuilder.Options);
}
}
DbContext.Summary of Steps:
IDesignTimeDbContextFactory implementation and connection string.References:
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In ABP, local events (ILocalEventHandler<T>) are only published and handled within the same application boundary and are not automatically forwarded to the distributed event bus. For distributed event handling (IDistributedEventHandler<T>), you must explicitly publish events as ETOs (Event Transfer Objects) designed for cross-service communication. The IdentityUserOrganizationUnit and IdentityUserRole entities do not have built-in ETOs, so their changes are not automatically published to the distributed event bus. To enable distributed eventing for these entities, you should:
Regarding performance: The default ABP implementation triggers a local event for every single assignment or removal, which can cause performance issues when processing hundreds of roles or organization units. Best practices to improve performance in such scenarios include:
Example: Custom ETO and Manual Publishing
public class UserRolesChangedEto
{
public Guid UserId { get; set; }
public List<Guid> AddedRoleIds { get; set; }
public List<Guid> RemovedRoleIds { get; set; }
}
// When updating user roles:
await _distributedEventBus.PublishAsync(new UserRolesChangedEto
{
UserId = userId,
AddedRoleIds = addedRoles,
RemovedRoleIds = removedRoles
});
For more details:
These approaches will help you optimize event handling and improve user transaction performance in high-volume scenarios.
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To correctly implement multiple Areas for controllers and use static client proxies across microservices in ABP, you need to ensure that the static proxy generation and registration align with the remote service configuration and the way your controllers are grouped.
Static Proxy Generation and Remote Service Names
AddStaticHttpClientProxies with a specific remote service name (e.g., "ServiceA" or "ServiceB"), ABP expects a corresponding entry in your appsettings.json under RemoteServices."ServiceA" and "ServiceB" in the same module, but only have a configuration for "ServiceA", ABP will throw an error when trying to resolve "ServiceB".Proxy Generation for Multiple Areas
[Area("ServiceA")], [Area("ServiceB")]), and you want to generate proxies for both, you must:
appsettings.json (or equivalent configuration) contains a RemoteServices entry for each area you register.Example appsettings.json:
"RemoteServices": {
"ServiceA": {
"BaseUrl": "https://localhost:44444/"
},
"ServiceB": {
"BaseUrl": "https://localhost:44444/"
}
}
context.Services.AddStaticHttpClientProxies(
typeof(ServiceAApplicationContractsModule).Assembly,
"ServiceA");
context.Services.AddStaticHttpClientProxies(
typeof(ServiceAApplicationContractsModule).Assembly,
"ServiceB");
abp generate-proxy -m ServiceA -t csharp -u https://localhost:44444/ --without-contracts
abp generate-proxy -m ServiceB -t csharp -u https://localhost:44444/ --without-contracts
"ServiceB") but do not provide a configuration for it, ABP will throw an error at runtime.AddStaticHttpClientProxies has a corresponding entry in your configuration.This approach is required because ABP's static proxy system uses the remote service name to resolve endpoints and API descriptions, and each must be explicitly configured.
Sources:
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IQuizQuestionCategoriesAppService). This usually means the backend API for the entity was not properly generated, registered, or exposed.To resolve this:
Ensure the Application and HTTP API layers are built and referenced correctly:
Rebuild the solution and ensure all migrations are applied if you added new entities.
Check that your new AppService is decorated with the [RemoteService] attribute (or not explicitly disabled).
Make sure the module dependencies are correct and the new module is added to your main module's DependsOn attribute.
If you are using a microservice or modular solution, ensure the service is exposed in the correct host.
Remove and re-add the solution in ABP Suite to refresh its internal cache.
If you have a custom folder structure, align it with the default ABP template.
For more details and troubleshooting steps, see:
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In ABP, when a transactional Unit of Work (UoW) is started (the default for non-GET requests), a database transaction is opened at the beginning of the request and remains open until the UoW is completed (typically at the end of the request or when CompleteAsync is called). This means that if you perform long-running operations (such as calling external APIs) inside the UoW, the transaction and any associated table locks will be held for the entire duration, potentially causing blocking and timeouts in the database.
The transaction is not only held during SaveChangesAsync; it is held for the entire lifetime of the UoW. SaveChangesAsync persists changes to the database, but the transaction is only committed when CompleteAsync is called. If the UoW is open while waiting for external services, the transaction remains open, and locks may be held, leading to performance issues and blocking.
To avoid this, you should minimize the time a transaction is held. One recommended approach is to perform external API calls and other long-running operations outside the transactional UoW. Only wrap the actual database operations in a short-lived UoW/transaction. For example:
// Fetch data from external API (outside UoW)
var externalData = await externalService.GetDataAsync();
// Start UoW only for DB operations
using (var uow = _unitOfWorkManager.Begin(isTransactional: true))
{
// Insert/update entities
await _repository.UpdateAsync(...);
await uow.CompleteAsync();
}
Sources:
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The ABP distributed lock (IAbpDistributedLock.TryAcquireAsync) is designed to prevent concurrent access to shared resources. However, if the second thread does not wait for the first to finish, it is likely because TryAcquireAsync returns immediately if the lock is already held, instead of waiting for it to be released.
By default, TryAcquireAsync uses a TimeSpan.Zero timeout, which means it will not wait if the lock is unavailable. To make the second thread wait, you must specify a non-zero timeout value.
In your code, you are passing TimeSpan.FromMinutes(5) as the timeout, which should make the second thread wait up to 5 minutes to acquire the lock. If the lock is not acquired within this period, handle will be null.
Ensure that:
"api-lock") is exactly the same for all threads.Example usage:
await using var handle = await _distributedLock.TryAcquireAsync("api-lock", TimeSpan.FromMinutes(5));
if (handle != null)
{
// Critical section: only one thread can enter here at a time
// Perform your database insert or API call
}
else
{
// Could not acquire the lock within the timeout
Logger.LogWarning("Could not acquire distributed lock.");
}
If you want the second thread to always wait until the lock is available, use a sufficiently large timeout or loop with retries.
Also, make sure you are not disposing the lock handle before your critical section is complete.
Sources:
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The error System.IO.FileNotFoundException: Could not load file or assembly 'Volo.Abp.BackgroundWorkers.Hangfire' indicates that the Hangfire dashboard is trying to load a background worker type from the assembly Volo.Abp.BackgroundWorkers.Hangfire, but this assembly is missing from your application.
This typically happens if you previously used the Volo.Abp.BackgroundWorkers.Hangfire package, registered background workers with it, and then removed the package or related code, but there are still jobs in the Hangfire database referencing types from that assembly.
How to resolve:
dotnet add package Volo.Abp.BackgroundWorkers.Hangfire
Clean Up Old Jobs (If You No Longer Use That Worker):
[HangFire].[Job], [HangFire].[State], etc.) in your database that reference the missing type.Prevent Future Issues:
Summary:
Either restore the missing assembly or clean up the orphaned jobs in your Hangfire database to resolve the dashboard error.
Sources:
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Yes, ABP Framework supports building solutions that target multiple platforms (web, mobile, and desktop) from a single code base by leveraging its modular architecture and solution templates.
When you generate a new solution using the ABP CLI or ABP Suite, you can select options to include:
The recommended approach is to use the "Layered" solution template, which allows you to include a mobile application (MAUI or React Native) fully integrated with your backend and other ABP modules. The solution structure will typically include:
You can generate such a solution using the ABP CLI:
abp new MySolution -t app-pro
During the creation process, you can select to include MAUI (for mobile/desktop) and web UIs.
Sources:
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