> ## Documentation Index
> Fetch the complete documentation index at: https://docs.smartbills.io/llms.txt
> Use this file to discover all available pages before exploring further.

# Installation

> How to install and configure the Smartbills .NET SDK

## Prerequisites

* .NET 6.0 or later
* A Smartbills account with an API key
* NuGet package manager (included with .NET SDK)

## Install via NuGet

<CodeGroup>
  ```bash .NET CLI theme={null}
  dotnet add package Smartbills.SDK
  ```

  ```bash Package Manager Console theme={null}
  Install-Package Smartbills.SDK
  ```

  ```xml PackageReference theme={null}
  <PackageReference Include="Smartbills.SDK" Version="*" />
  ```
</CodeGroup>

### ASP.NET Core Integration

For ASP.NET Core applications, install the companion package for dependency injection support:

```bash theme={null}
dotnet add package Smartbills.SDK.AspNetCore
```

## Configuration

### Basic Configuration

```csharp theme={null}
using Smartbills.SDK;

var client = new SmartbillsClient(new SmartbillsClientOptions
{
    AccessToken = "YOUR_API_KEY",
    BusinessId = 123
});
```

### Configuration Options

| Option        | Type     | Required | Description                          |
| ------------- | -------- | -------- | ------------------------------------ |
| `AccessToken` | `string` | Yes      | Your Smartbills API access token     |
| `BusinessId`  | `long`   | Yes      | The ID of the business to operate on |

### ASP.NET Core Dependency Injection

When using the `Smartbills.SDK.AspNetCore` package, register the client in your `Program.cs` or `Startup.cs`:

```csharp theme={null}
using Smartbills.SDK;
using Smartbills.SDK.AspNetCore;

builder.Services.AddSmartbills(options =>
{
    options.AccessToken = builder.Configuration["Smartbills:AccessToken"];
    options.BusinessId = long.Parse(builder.Configuration["Smartbills:BusinessId"]);
});
```

Then inject the client into your services:

```csharp theme={null}
public class InvoiceService
{
    private readonly IInvoiceClient _invoiceClient;

    public InvoiceService(IInvoiceClient invoiceClient)
    {
        _invoiceClient = invoiceClient;
    }

    public async Task<SBInvoice> GetInvoiceAsync(long id)
    {
        return await _invoiceClient.GetByIdAsync(id);
    }
}
```

You can also inject the top-level client:

```csharp theme={null}
public class BillingService
{
    private readonly SmartbillsClient _client;

    public BillingService(SmartbillsClient client)
    {
        _client = client;
    }

    public async Task<SBInvoiceSummary> GetSummaryAsync(CancellationToken ct)
    {
        return await _client.Invoices.GetSummaryAsync(ct: ct);
    }
}
```

### Environment Configuration

Store your credentials securely using `appsettings.json` or environment variables:

```json appsettings.json theme={null}
{
  "Smartbills": {
    "AccessToken": "YOUR_API_KEY",
    "BusinessId": "123"
  }
}
```

For environment-specific overrides:

```json appsettings.Development.json theme={null}
{
  "Smartbills": {
    "AccessToken": "sk_test_dev_key_here"
  }
}
```

<Warning>
  Never commit API keys to source control. Use environment variables, user secrets, or a vault service for production deployments.
</Warning>

### User Secrets (Development)

For local development, use the .NET user secrets manager:

```bash theme={null}
dotnet user-secrets set "Smartbills:AccessToken" "sk_test_your_key"
dotnet user-secrets set "Smartbills:BusinessId" "123"
```

## Per-Request Options

Every method accepts an optional `SBRequestOptions` parameter to override default settings for individual requests:

```csharp theme={null}
var options = new SBRequestOptions
{
    // Override settings for this specific request
};

var invoice = await client.Invoices.GetByIdAsync(42, options);
```

## Verifying Installation

Create a simple console application to verify the SDK is working:

```csharp theme={null}
using Smartbills.SDK;

var client = new SmartbillsClient(new SmartbillsClientOptions
{
    AccessToken = "YOUR_API_KEY",
    BusinessId = 123
});

try
{
    var summary = await client.Invoices.GetSummaryAsync();
    Console.WriteLine("Connection successful!");
    Console.WriteLine($"Invoice summary retrieved.");
}
catch (Exception ex)
{
    Console.WriteLine($"Error: {ex.Message}");
}
```

## Next Steps

<Card title="Usage Guide" icon="book" href="/sdks/dotnet/usage">
  Learn how to use InvoiceClient, FileClient, and BillingClient
</Card>