BeforeEntityUpdate

The BeforeEntityUpdate command handler lets you execute custom logic before an entity is updated. You can use it to:

• Validate entity data

• Initialize or modify fields

• Log changes or perform custom actions

This command can be implemented both in the API project (server-side) and in the Blazor UI project (client-side).

If you don’t implement a BeforeEntityUpdate handler, Bloqs will still update the entity normally. Implementing it allows you to enforce rules and logic before the update happens.

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How to Implement

1. Create a class and mark it with [EntityCommandHandler<T>], where T is your entity type.

2. Implement ICommandHandler<BeforeEntityUpdateCommand, BeforeEntityUpdateCommandResult>.

3. Override the HandleAsync method and write your custom logic.

4. Throw an exception if the entity is invalid — this will prevent the update.

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API Example

using Bloqs.App.Engine.Commands; 
using Bloqs.App.Engine.Commands.Before;
using Templates.SampleApp.Models;
using Templates.SampleApp.Models.Data;

namespace Templates.SampleApp.Api.Commands.Activities;

[EntityCommandHandler<Activity>]
public class BeforeActivityUpdate
    : ICommandHandler<BeforeEntityUpdateCommand, BeforeEntityUpdateCommandResult>
{
    public Task<BeforeEntityUpdateCommandResult> HandleAsync(
        BeforeEntityUpdateCommand command,
        CancellationToken cancellationToken = default
    )
    {
        var activity = (Activity)command.DataEntities.First();

        Console.WriteLine($"{AppConstants.App.Name} [API]: BeforeActivityUpdate: " + activity.Name);

        if (string.IsNullOrEmpty(activity.Name))
        {
            throw new Exception("Invalid activity Name");
        }

        return Task.FromResult(BeforeEntityUpdateCommandResult.CreateSuccess());
    }
}

• Runs server-side in the API project.

• Executes before the entity is persisted to storage.

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UI Example

using Bloqs.App.Engine.Commands;
using Bloqs.App.Engine.Commands.Before;
using Templates.SampleApp.Models;
using Templates.SampleApp.Models.Data;

namespace Templates.SampleApp.UserInterface.Commands;

[EntityCommandHandler<Activity>]
public class BeforeActivityUpdate
    : ICommandHandler<BeforeEntityUpdateCommand, BeforeEntityUpdateCommandResult>
{
    public Task<BeforeEntityUpdateCommandResult> HandleAsync(
        BeforeEntityUpdateCommand command,
        CancellationToken cancellationToken = default
    )
    {
        var activity = (Activity)command.DataEntities.First();

        Console.WriteLine($"{AppConstants.App.Name} [UI]: BeforeActivityUpdate: " + activity.Name);

        if (activity.Name == "-")
        {
            throw new Exception("Invalid activity Name");
        }

        return Task.FromResult(BeforeEntityUpdateCommandResult.CreateSuccess());
    }
}

• Runs client-side in Blazor WASM.

• Provides early validation and immediate feedback before sending data to the API.

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Key Points

• Both API and UI handlers can coexist for layered validation.

• The command.DataEntities collection contains the entities being updated.

• You can throw exceptions to prevent the update if validation fails.

• You can modify entity fields before they are persisted.

• The EntityCommandHandler attribute is required to register the handler in the Bloqs system.

• Useful for enforcing business rules, validation, or logging before the database is updated.

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This handler ensures that your entities meet all requirements before they are saved, giving you control over data integrity and business logic.