DataFuse

Like GraphQL, but for your heterogeneous backend systems

DataFuse is a declarative framework that aggregates data from SQL databases, REST APIs, and any heterogeneous datsource into unified, strongly-typed objects — replacing hundreds of lines of manual orchestration code with clean, schema-driven configuration.

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The Problem

Building a product page? You need inventory from SQL Server, pricing from a REST API, and reviews from an external service. That's 50+ lines of manual fetch-assemble code — sequential, tightly coupled, and repeated across your codebase.

// Without DataFuse: manual orchestration everywhere
var product = await db.QueryFirstAsync<ProductRecord>("SELECT * FROM Products WHERE Id = @Id", new { Id = productId });
var pricing = await httpClient.GetFromJsonAsync<PricingResponse>($"https://pricing-api/products/{productId}");
var reviews = await httpClient.GetFromJsonAsync<ReviewResponse[]>($"https://reviews-api/products/{productId}");

product.Price = pricing.Price;
product.Reviews = reviews.Select(r => new Review { Rating = r.Stars, Comment = r.Text }).ToArray();

The Solution

// With DataFuse: declare once, use everywhere
var product = dataProvider.GetData(new ProductRequest { ProductId = 42 });

DataFuse automatically executes the SQL query first, then runs pricing and reviews API calls in parallel, passes parent results to child queries, and assembles the final typed object.

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Quick Start

1. Install

dotnet add package DataFuse.Integration
dotnet add package DataFuse.Adapters.SQL       # SQL with Dapper
dotnet add package DataFuse.Adapters.WebAPI     # REST APIs

2. Define Your Entity

public class Product : IEntity
{
    public int ProductId { get; set; }
    public string Name { get; set; }
    public decimal Price { get; set; }
    public Review[] Reviews { get; set; }
}

3. Create Queries

// SQL query — fetches product from database
public class ProductQuery : SQLQuery<ProductResult>
{
    protected override Func<IDbConnection, Task<ProductResult>> GetQuery(
        IDataContext context, IQueryResult parentQueryResult)
    {
        var request = (ProductRequest)context.Request;
        return connection => connection.QueryFirstOrDefaultAsync<ProductResult>(
            "SELECT ProductId as Id, Name, Price FROM Products WHERE ProductId = @Id",
            new { Id = request.ProductId });
    }
}

// API query — fetches reviews from external service, receives parent result
public class ReviewsApiQuery : WebQuery<CollectionResult<ReviewResult>>
{
    public ReviewsApiQuery() : base("https://api.reviews.com/") { }

    protected override Func<Uri> GetQuery(IDataContext context, IQueryResult parentQueryResult)
    {
        var product = (ProductResult)parentQueryResult;
        return () => new Uri($"products/{product.Id}/reviews", UriKind.Relative);
    }
}

4. Create Transformers

public class ProductTransform : BaseTransformer<ProductResult, Product>
{
    public override void Transform(ProductResult queryResult, Product entity)
    {
        entity.ProductId = queryResult.Id;
        entity.Name = queryResult.Name;
        entity.Price = queryResult.Price;
    }
}

public class ReviewsTransform : BaseTransformer<CollectionResult<ReviewResult>, Product>
{
    public override void Transform(CollectionResult<ReviewResult> queryResult, Product entity)
    {
        entity.Reviews = queryResult?.Select(r => new Review
        {
            ReviewId = r.Id, Comment = r.Comment, Rating = r.Rating
        }).ToArray() ?? Array.Empty<Review>();
    }
}

5. Configure the Schema

public class ProductConfiguration : EntityConfiguration<Product>
{
    public override IEnumerable<Mapping<Product, IQueryResult>> GetSchema()
    {
        return CreateSchema.For<Product>()
            .Map<ProductQuery, ProductTransform>(For.Paths("product"),
                product => product.Dependents
                    .Map<ReviewsApiQuery, ReviewsTransform>(For.Paths("product/reviews")))
            .End();
    }
}

6. Register & Use

// DI registration
services.UseDataFuse()
    .WithEngine(c => new QueryEngine(sqlConfiguration))
    .WithEngine<DataFuse.Adapters.WebAPI.QueryEngine>()
    .WithPathMatcher(c => new XPathMatcher())
    .WithEntityConfiguration<Product>(c => new ProductConfiguration());

services.AddHttpClient();

// Usage — one line to get fully hydrated data
public class ProductService
{
    private readonly IDataProvider<Product> _dataProvider;

    public ProductService(IDataProvider<Product> dataProvider) => _dataProvider = dataProvider;

    public Product GetProduct(int productId)
        => _dataProvider.GetData(new ProductRequest { ProductId = productId });

    // Selective loading — only fetch product + reviews, skip other paths
    public Product GetProductWithReviews(int productId)
        => _dataProvider.GetData(new ProductRequest
        {
            ProductId = productId,
            SchemaPaths = new[] { "product", "product/reviews" }
        });
}

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Key Features

Feature	Description
Declarative Schema	Define data relationships once with fluent configuration
Automatic Parallelism	Sibling queries run in parallel — no Task.WhenAll boilerplate
Selective Loading	Fetch only the data paths the consumer needs via SchemaPaths
Parent-Child Dependencies	Parent results flow to child queries automatically
Cross-Source Mixing	Combine SQL + REST API + EF Core queries in one entity
Type Safety	Strongly-typed queries, results, and transformers
Built-in Caching	[CacheResult] attribute for expensive query results
Custom Adapters	Add any data source by implementing IQueryEngine

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Packages

Package	Purpose	Install
DataFuse.Integration	Core orchestration, DI, helpers	dotnet add package DataFuse.Integration
DataFuse.Adapters.SQL	SQL via Dapper	dotnet add package DataFuse.Adapters.SQL
DataFuse.Adapters.EntityFramework	EF Core	dotnet add package DataFuse.Adapters.EntityFramework
DataFuse.Adapters.WebAPI	REST APIs via HttpClient	dotnet add package DataFuse.Adapters.WebAPI
DataFuse.Adapters.Abstraction	Interfaces & base classes	Included as dependency

Compatibility

Package	.NET	.NET Standard	.NET Framework
DataFuse.Integration	9.0+	2.0, 2.1	4.6.2+
DataFuse.Adapters.SQL	9.0+	2.1	4.6.2+
DataFuse.Adapters.EntityFramework	9.0+	-	-
DataFuse.Adapters.WebAPI	9.0+	2.0, 2.1	4.6.2+

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Documentation

See the Complete Developer Guide for detailed documentation including:

• Real-world use cases (e-commerce, customer 360, reporting)
• Core concepts deep dive
• Query implementation guides (SQL, EF Core, Web API)
• Transformer patterns
• Advanced features (caching, selective loading, custom engines)
• Architecture overview

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Support

If you are having problems, please let us know by raising a new issue.

License

This project is licensed with the MIT license.

Version History

The main branch is now on .NET 9.0. Previous versions:

Version	Release Notes	Developer Guide
v2.0.0	Notes	Guide
v1.0.0	Notes	Guide