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

# .NET SDK

> Official .NET SDK for Blindfold — detect, tokenize, mask, redact, hash, encrypt, and synthesize PII

## Installation

```bash theme={null}
dotnet add package Blindfold.Sdk
```

**Zero external dependencies** — uses only built-in .NET libraries (System.Text.Json).

Targets `net6.0`, `net8.0`, and `netstandard2.1`.

## Quick Start (Local Mode)

No API key needed — runs entirely in-process with 86 regex-based entity types.

```csharp theme={null}
using Blindfold.Sdk;

using var client = new BlindfoldClient();  // no API key needed

var result = await client.DetectAsync("Email john@acme.com, SSN 123-45-6789");

foreach (var entity in result.DetectedEntities)
{
    Console.WriteLine($"{entity.Type}: {entity.Text}");
}
// Email Address: john@acme.com
// Social Security Number: 123-45-6789
```

## Cloud API Setup

For NLP-powered detection (names, addresses, organizations), compliance policies, and audit logs:

```csharp theme={null}
using Blindfold.Sdk;

// Simple initialization
using var client = new BlindfoldClient("your-api-key");

// Full configuration
using var client = new BlindfoldClient(new BlindfoldOptions
{
    ApiKey = "your-api-key",
    Region = "eu",                          // "eu" (default) or "us"
    MaxRetries = 3,
    Timeout = TimeSpan.FromSeconds(30),
    UserId = "user-123",                    // optional user tracking
});
```

## Methods

All methods are async with `Async` suffix and accept an optional `CancellationToken` parameter. The client implements `IDisposable`.

### DetectAsync

Identify PII without modifying the text.

```csharp theme={null}
var result = await client.DetectAsync("Contact John Doe at john@example.com");

Console.WriteLine(result.EntitiesCount);  // 2

foreach (var entity in result.DetectedEntities)
{
    Console.WriteLine($"{entity.Type}: {entity.Text} ({entity.Score:F2})");
}
```

### TokenizeAsync / Detokenize

Replace PII with reversible tokens, then restore.

```csharp theme={null}
// Tokenize
var response = await client.TokenizeAsync(
    "Contact John Doe at john@example.com"
);

Console.WriteLine(response.Text);
// "Contact <Person_1> at <Email Address_1>"

Console.WriteLine(response.Mapping);
// {<Person_1>: John Doe, <Email Address_1>: john@example.com}

// Detokenize (sync — runs client-side, no API call)
var original = client.Detokenize(
    response.Text,
    response.Mapping
);

Console.WriteLine(original.Text);
// "Contact John Doe at john@example.com"
```

### RedactAsync

Permanently remove PII from text.

```csharp theme={null}
var result = await client.RedactAsync(
    "Patient Jane Smith, SSN: 123-45-6789"
);

Console.WriteLine(result.Text);
// "Patient , SSN: "
```

### MaskAsync

Partially hide PII while keeping some characters visible.

```csharp theme={null}
var result = await client.MaskAsync(
    "Card: 4532-7562-9102-3456",
    charsToShow: 4,       // chars to show
    fromEnd: true,         // from end
    maskChar: "*",         // masking character
    entities: null         // entities filter (null = all)
);

Console.WriteLine(result.Text);
// "Card: ***************3456"
```

### HashAsync

Create deterministic identifiers for analytics.

```csharp theme={null}
var result = await client.HashAsync(
    "User john@example.com purchased item",
    hashType: "SHA-256",    // hash type
    prefix: "user_",        // prefix
    hashLength: 16,         // hash length
    entities: null           // entities filter
);

Console.WriteLine(result.Text);
// "User user_a3f8b9c2d4e5f6g7 purchased item"
```

### EncryptAsync

Encrypt PII using AES-256.

```csharp theme={null}
var result = await client.EncryptAsync(
    "API Key: sk-1234567890abcdef",
    "your-secure-key-min-16-chars"
);

Console.WriteLine(result.Text);
// "API Key: gAAAAABh3K7x..."
```

### SynthesizeAsync

Replace PII with realistic fake data.

```csharp theme={null}
var result = await client.SynthesizeAsync(
    "John Doe lives in New York",
    language: "en",    // language
    entities: null     // entities filter
);

Console.WriteLine(result.Text);
// "Michael Smith lives in Boston" (example - will vary)
```

## Batch Processing

Process multiple texts in a single call.

```csharp theme={null}
var texts = new[]
{
    "Contact John Doe",
    "Email jane@example.com",
    "No PII here"
};

var result = await client.TokenizeBatchAsync(texts);

Console.WriteLine(result.Total);      // 3
Console.WriteLine(result.Succeeded);  // 3

foreach (var item in result.Results)
{
    Console.WriteLine(item.Text);
}
```

All methods have batch variants: `DetectBatchAsync`, `TokenizeBatchAsync`, `RedactBatchAsync`, `MaskBatchAsync`, `HashBatchAsync`, `EncryptBatchAsync`, `SynthesizeBatchAsync`.

## Entity Filtering

Only detect specific entity types:

```csharp theme={null}
var result = await client.DetectAsync(
    "John Doe, SSN 123-45-6789, email john@example.com",
    entities: new[] { "Social Security Number", "Email Address" }
);
// Only SSN and email detected, name is ignored
```

## Error Handling

```csharp theme={null}
using Blindfold.Sdk.Errors;

try
{
    var result = await client.TokenizeAsync("...");
}
catch (AuthenticationException ex)
{
    // Invalid API key (401)
    Console.Error.WriteLine("Invalid API key");
}
catch (ApiException ex)
{
    // API error (validation, rate limit, etc.)
    Console.Error.WriteLine($"API error {ex.StatusCode}");
}
catch (NetworkException ex)
{
    // Connection issues
    Console.Error.WriteLine($"Network error: {ex.Message}");
}
```

## Locales

Configure country-specific entity detection:

```csharp theme={null}
using var client = new BlindfoldClient(new BlindfoldOptions
{
    Locales = new[] { "us", "de", "fr" }
});
```

Available locales: `us`, `uk`, `eu`, `de`, `fr`, `es`, `it`, `pt`, `pl`, `cz`, `sk`, `ru`, `nl`, `ro`, `dk`, `se`, `no`, `be`, `at`, `ie`, `fi`, `hu`, `bg`, `hr`, `si`, `lt`, `lv`, `ee`, `ca`, `ch`, `au`, `nz`, `in`, `jp`, `kr`, `za`, `tr`, `il`, `ar`, `cl`, `co`, `br`

## Source Code

<Card title="GitHub Repository" icon="github" href="https://github.com/blindfold-dev/Blindfold/tree/main/packages/dotnet-sdk">
  Full source code, API reference, and additional examples.
</Card>