---
title: "What is CQRS and how would you implement it in a .NET application?"  
description: "CQRS (Command Query Responsibility Segregation) is a software architecture pattern that separates the responsibilities of reading data (queries) and w"  
author: "ICSM Computer"  
published: 2025-06-16  
updated: 2025-06-16  
canonical: https://www.mindstick.com/articles/339604/what-is-cqrs-and-how-would-you-implement-it-in-a-dot-net-application  
category: "c#"  
tags: ["c#"]  
reading_time: 3 minutes  

---

# What is CQRS and how would you implement it in a .NET application?

> **CQRS (Command Query [Responsibility](https://answers.mindstick.com/qa/104498/what-is-the-significance-of-the-fiscal-responsibility-and-budget-management-act) Segregation)** is a [software architecture](https://www.mindstick.com/articles/337598/define-the-importance-of-microservices-in-modern-software-architecture) pattern that separates the [responsibilities](https://yourviews.mindstick.com/view/82654/a-basket-full-of-responsibilities) of **[reading data](https://www.mindstick.com/forum/12915/how-to-embed-asp-dot-net-with-sql-server-reading-data-and-changing-textbox-field)** (queries) and **writing data** (commands) into distinct models. This improves [scalability](https://www.mindstick.com/interview/784/what-are-the-performance-and-scalability-characteristics-of-mysql), performance, and maintainability, especially in complex domains.

### What is CQRS?

- **Commands**: Modify state (create, update, delete). They return **void** or a simple result (e.g., success/failure).
- **Queries**: Read data. They do **not** modify state and [return data](https://www.mindstick.com/forum/157891/what-is-the-role-of-the-jsonresult-class-in-mvc-how-can-it-use-to-return-data-to-an-ajax-request) (DTOs).
- **Segregation**: By splitting these concerns, each side can be optimized independently — e.g., read model could use denormalized views for performance.

![What is CQRS and how would you implement it in a .NET application?](https://www.mindstick.com/mindstickarticle/36bb03e9-6481-4a3f-8daa-c08f3b3a453c/images/658d6f21-34d9-437e-995b-b4dfc7c0d685.jpg)

### Why Use CQRS?

- Clear separation of concerns (read vs write logic)
- Easier to scale reads and writes independently
- Enables [complex business](https://www.mindstick.com/forum/161972/is-sql-more-vital-for-solving-complex-business-problems-or-power-bi-tableau-for-insights) logic on writes without polluting queries
- Simplifies event sourcing and audit trails

### How to Implement CQRS in .NET

#### 1. Define Command and Query Models

```cs
// Command
public class CreateStudentCommand
{
    public string Name { get; set; }
    public string Email { get; set; }
}

// Query
public class GetStudentByIdQuery
{
    public long Id { get; set; }
}
```

#### 2. Create Handlers for Each

```cs
public class CreateStudentCommandHandler
{
    private readonly AppDbContext _context;

    public CreateStudentCommandHandler(AppDbContext context)
    {
        _context = context;
    }

    public async Task<bool> Handle(CreateStudentCommand command)
    {
        var student = new Student
        {
            Name = command.Name,
            Email = command.Email
        };

        _context.Students.Add(student);
        await _context.SaveChangesAsync();
        return true;
    }
}
```

```cs
public class GetStudentByIdQueryHandler
{
    private readonly AppDbContext _context;

    public GetStudentByIdQueryHandler(AppDbContext context)
    {
        _context = context;
    }

    public async Task<StudentDto> Handle(GetStudentByIdQuery query)
    {
        return await _context.Students
            .Where(s => s.Id == query.Id)
            .Select(s => new StudentDto
            {
                Id = s.Id,
                Name = s.Name,
                Email = s.Email
            })
            .FirstOrDefaultAsync();
    }
}
```

#### 3. Optional: Use Mediator Pattern (e.g., with MediatR)

```cs
dotnet add package MediatR.Extensions.Microsoft.DependencyInjection
```

Define command and handler:

```cs
public record CreateStudentCommand(string Name, string Email) : IRequest<bool>;

public class CreateStudentCommandHandler : IRequestHandler<CreateStudentCommand, bool>
{
    private readonly AppDbContext _context;

    public CreateStudentCommandHandler(AppDbContext context) => _context = context;

    public async Task<bool> Handle(CreateStudentCommand request, CancellationToken cancellationToken)
    {
        _context.Students.Add(new Student { Name = request.Name, Email = request.Email });
        await _context.SaveChangesAsync();
        return true;
    }
}
```

### CQRS + Event Sourcing (Advanced Use Case)

For even more decoupling, commands can raise events which are stored and later replayed to rebuild the system state. Libraries like **EventStoreDB** or **NEventStore** can be used.

![What is CQRS and how would you implement it in a .NET application?](https://www.mindstick.com/mindstickarticle/36bb03e9-6481-4a3f-8daa-c08f3b3a453c/images/5b103003-27a4-4807-a855-21cb6b2b5d5c.png)

### When to Use CQRS

| Use CQRS When... | Avoid CQRS When... |
| --- | --- |
| Complex domains with many business rules | Simple CRUD apps |
| Need to scale reads/writes independently | Small teams or tight deadlines |
| Heavy read [operations](https://answers.mindstick.com/qa/34054/who-has-taken-charge-as-the-new-director-general-of-military-operations-dgmo-of-the-indian-army) with different needs | One model suffices for read & write |

---

Original Source: https://www.mindstick.com/articles/339604/what-is-cqrs-and-how-would-you-implement-it-in-a-dot-net-application

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