C# / .NET

# Uses System.Net.Http.HttpClient — built into .NET 6+
# No NuGet packages required
# For JSON serialisation: System.Text.Json (also built in)

// Models/SchemaCheck.cs
using System.Text.Json.Serialization;

public record SchemaCheckResult(
    [property: JsonPropertyName("success")] bool Success,
    [property: JsonPropertyName("url")] string? Url,
    [property: JsonPropertyName("schemas_found")] int SchemasFound,
    [property: JsonPropertyName("schemas")] List<Schema> Schemas,
    [property: JsonPropertyName("summary")] Summary Summary,
    [property: JsonPropertyName("meta")] Meta Meta
);

public record Schema(
    [property: JsonPropertyName("type")] string Type,
    [property: JsonPropertyName("valid")] bool Valid,
    [property: JsonPropertyName("rich_result_eligible")] bool RichResultEligible,
    [property: JsonPropertyName("deprecated")] bool Deprecated,
    [property: JsonPropertyName("errors")] List<Issue> Errors,
    [property: JsonPropertyName("warnings")] List<Issue> Warnings,
    [property: JsonPropertyName("properties_found")] List<string> PropertiesFound,
    [property: JsonPropertyName("properties_missing_required")] List<string> PropertiesMissingRequired,
    [property: JsonPropertyName("rich_result")] RichResult RichResult
);

public record Issue(
    [property: JsonPropertyName("severity")] string Severity,
    [property: JsonPropertyName("property")] string Property,
    [property: JsonPropertyName("message")] string Message,
    [property: JsonPropertyName("fix")] string Fix,
    [property: JsonPropertyName("google_docs_url")] string GoogleDocsUrl
);

public record RichResult(
    [property: JsonPropertyName("eligible")] bool Eligible,
    [property: JsonPropertyName("reason")] string Reason
);

public record Summary(
    [property: JsonPropertyName("total_schemas")] int TotalSchemas,
    [property: JsonPropertyName("valid_schemas")] int ValidSchemas,
    [property: JsonPropertyName("invalid_schemas")] int InvalidSchemas,
    [property: JsonPropertyName("total_errors")] int TotalErrors,
    [property: JsonPropertyName("total_warnings")] int TotalWarnings,
    [property: JsonPropertyName("rich_result_eligible")] int RichResultEligible,
    [property: JsonPropertyName("score")] int Score
);

public record Meta(
    [property: JsonPropertyName("api_version")] string ApiVersion,
    [property: JsonPropertyName("validated_at")] string ValidatedAt,
    [property: JsonPropertyName("cached")] bool Cached,
    [property: JsonPropertyName("credits_used")] int CreditsUsed,
    [property: JsonPropertyName("credits_remaining")] int CreditsRemaining,
    [property: JsonPropertyName("response_time_ms")] int ResponseTimeMs
);

// Services/SchemaCheckService.cs
using System.Net.Http.Json;
using System.Text.Json;
using System.Web;

public class SchemaCheckService
{
    private readonly HttpClient _http;
    private readonly string _apiKey;

    public SchemaCheckService(HttpClient http, string apiKey)
    {
        _http   = http;
        _apiKey = apiKey;
    }

    public async Task<SchemaCheckResult> ValidateUrlAsync(string url)
    {
        var query = HttpUtility.ParseQueryString(string.Empty);
        query["url"]        = url;
        query["access_key"] = _apiKey;

        var endpoint = $"https://schemacheck.dev/api/v1/validate?{query}";
        var response = await _http.GetAsync(endpoint);
        var body     = await response.Content.ReadAsStringAsync();

        if (!response.IsSuccessStatusCode)
        {
            var err = JsonDocument.Parse(body).RootElement
                .GetProperty("error");
            throw new Exception($"[{err.GetProperty("code")}] {err.GetProperty("message")}");
        }

        return JsonSerializer.Deserialize<SchemaCheckResult>(body)!;
    }
}

// Program.cs — example usage
var client  = new HttpClient();
var service = new SchemaCheckService(client, Environment.GetEnvironmentVariable("SCHEMACHECK_API_KEY")!);

var result = await service.ValidateUrlAsync("https://stripe.com");

Console.WriteLine($"Score: {result.Summary.Score}/100");
Console.WriteLine($"Schemas found: {result.SchemasFound}");

foreach (var schema in result.Schemas)
{
    Console.WriteLine($"\n[{schema.Type}] valid={schema.Valid} richResult={schema.RichResultEligible}");

    foreach (var error in schema.Errors)
    {
        Console.WriteLine($"  ✗ {error.Property}: {error.Message}");
        Console.WriteLine($"    Fix: {error.Fix}");
    }
}

using System.Net.Http.Json;
using System.Text.Json;

var apiKey = Environment.GetEnvironmentVariable("SCHEMACHECK_API_KEY")!;
var client = new HttpClient();
client.DefaultRequestHeaders.Add("x-api-key", apiKey);

var payload = new
{
    jsonld = new
    {
        @context      = "https://schema.org",
        @type         = "Article",
        headline      = "How to validate Schema.org structured data",
        author        = new { @type = "Person", name = "Jane Doe" },
        datePublished = "2026-03-18",
        image         = "https://example.com/photo.jpg",
    }
};

var response = await client.PostAsJsonAsync(
    "https://schemacheck.dev/api/v1/validate",
    payload
);

var body = await response.Content.ReadAsStringAsync();

if (!response.IsSuccessStatusCode)
{
    var err = JsonDocument.Parse(body).RootElement.GetProperty("error");
    throw new Exception($"[{err.GetProperty("code")}] {err.GetProperty("message")}");
}

var result = JsonSerializer.Deserialize<SchemaCheckResult>(body,
    new JsonSerializerOptions { PropertyNameCaseInsensitive = true })!;

var schema = result.Schemas[0];
if (!schema.Valid)
{
    foreach (var e in schema.Errors)
        Console.WriteLine($"Error: {e.Property}: {e.Fix}");
    Environment.Exit(1);
}

Console.WriteLine($"Valid! Rich result eligible: {schema.RichResultEligible}");

// Register as singleton in ASP.NET Core DI
// Program.cs
builder.Services.AddHttpClient<SchemaCheckService>(client =>
{
    client.DefaultRequestHeaders.Add(
        "x-api-key",
        builder.Configuration["SchemaCheck:ApiKey"]
    );
    client.BaseAddress = new Uri("https://schemacheck.dev/");
    client.Timeout = TimeSpan.FromSeconds(30);
});

// appsettings.json
{
  "SchemaCheck": {
    "ApiKey": "sc_live_your_key_here"
  }
}