---
title: 'Declaring Resources'
excerpt: 'Add databases, caches, and service references in AppHost with expandable code samples.'
icon: 'Database'
---

## Resource references

Aspire resources are added in AppHost and injected into consuming projects via `WithReference`.

```csharp title="AppHost/Program.cs"
var builder = DistributedApplication.CreateBuilder(args);

var postgres = builder.AddPostgres("postgres")
    .AddDatabase("catalog");

var api = builder.AddProject<Projects.CatalogApi>("catalog-api")
    .WithReference(postgres);

builder.AddProject<Projects.Storefront>("storefront")
    .WithReference(api);

builder.Build().Run();
```

## Manual install workflow

<InstallTabs>
  <InstallTab value="cli" label="CLI">
    <CommandBlock
      pnpm="dotnet add package Aspire.Hosting.PostgreSQL"
      npm="dotnet add package Aspire.Hosting.PostgreSQL"
      yarn="dotnet add package Aspire.Hosting.PostgreSQL"
      bun="dotnet add package Aspire.Hosting.PostgreSQL"
    />
  </InstallTab>
  <InstallTab value="manual" label="Manual">
    <Steps>
      <Step>Install dependencies</Step>

      ```xml title="AppHost/AppHost.csproj"
      <ItemGroup>
        <PackageReference Include="Aspire.Hosting.PostgreSQL" Version="9.0.0" />
        <PackageReference Include="Aspire.Hosting.Redis" Version="9.0.0" />
      </ItemGroup>
      ```

      <Step>Copy the AppHost bootstrap</Step>

      ```csharp title="AppHost/Program.cs"
      var builder = DistributedApplication.CreateBuilder(args);

      var postgres = builder.AddPostgres("postgres").AddDatabase("app");
      var cache = builder.AddRedis("cache");

      var api = builder.AddProject<Projects.ApiService>("api")
          .WithReference(postgres)
          .WithReference(cache);

      builder.AddProject<Projects.Web>("web")
          .WithReference(api);

      builder.Build().Run();
      ```
    </Steps>
  </InstallTab>
</InstallTabs>

## Connection string injection

Consuming projects receive configuration automatically:

```csharp title="ApiService/Program.cs"
builder.AddServiceDefaults();
builder.AddNpgsqlDbContext<CatalogContext>("catalog");
```

Long YAML configs also collapse cleanly:

```yaml title="aspire.yaml"
resources:
  postgres:
    type: postgres
    databases:
      - catalog
  redis:
    type: redis
  catalog-api:
    type: project
    path: ../CatalogApi
    references:
      - postgres
      - redis
  storefront:
    type: project
    path: ../Storefront
    references:
      - catalog-api
```