Connect Aspire apps to Data API Builder

⭐ Community Toolkit

This page describes how consuming apps connect to a Data API Builder resource. For configuration files, database references, image settings, and health checks, see Set up Data API Builder in the AppHost.

DAB has no dedicated Community Toolkit client package. It exposes standard REST and GraphQL endpoints, so use the HTTP or GraphQL client for your app’s language.

Connection values

DataApiBuilderContainerResource implements service discovery rather than a connection string. Referencing a DAB resource named dab injects:

Environment variable	Description
services__dab__http__0	Resolved URL for the DAB HTTP endpoint

The AppHost resource also exposes endpoint properties for building custom expressions. These are AppHost properties, not additional consuming-app environment variables. See Use endpoint properties for synchronized C# and TypeScript examples.

Nota

DAB doesn’t implement IResourceWithConnectionString, so referencing it does not create ConnectionStrings__dab.

Connect from your app

Each example calls the REST route /api/Product. Use /graphql for GraphQL requests.

C#

Apps that use Aspire service defaults can address the resource by name:

Program.cs

builder.Services.AddHttpClient("dab", client =>
{
    client.BaseAddress = new Uri("https+http://dab");
});

Or read the resolved service-discovery endpoint directly:

Program.cs

var endpoint = Environment.GetEnvironmentVariable("services__dab__http__0")
    ?? throw new InvalidOperationException(
        "services__dab__http__0 is not set.");

using var client = new HttpClient
{
    BaseAddress = new Uri(endpoint)
};

var products = await client.GetStringAsync("/api/Product");

TypeScript

Node.js includes fetch, so no DAB-specific package is required:

index.ts

const endpoint = process.env.services__dab__http__0;
if (!endpoint) {
  throw new Error('services__dab__http__0 is not set.');
}

const response = await fetch(new URL('/api/Product', endpoint));
if (!response.ok) {
  throw new Error(`DAB request failed: ${response.status}`);
}

const products = await response.json();

Python

Use urllib.request from the Python standard library:

app.py

import json
import os
from urllib.request import urlopen

endpoint = os.environ["services__dab__http__0"].rstrip("/")

with urlopen(f"{endpoint}/api/Product") as response:
    products = json.load(response)

Go

Use Go’s standard net/http package:

main.go

package main

import (
    "fmt"
    "io"
    "net/http"
    "os"
    "strings"
)

func main() {
    endpoint := strings.TrimRight(
        os.Getenv("services__dab__http__0"),
        "/",
    )
    if endpoint == "" {
        panic("services__dab__http__0 is not set")
    }

    response, err := http.Get(endpoint + "/api/Product")
    if err != nil {
        panic(err)
    }
    defer response.Body.Close()

    body, err := io.ReadAll(response.Body)
    if err != nil {
        panic(err)
    }

    fmt.Println(string(body))
}

See also

• REST API in Data API Builder
• GraphQL in Data API Builder
• Service discovery in Aspire
• Set up Data API Builder in the AppHost