Typed Variables with DTOs

Technical Preview

The C# SDK is a technical preview available from Camunda 8.9. It will become fully supported in Camunda 8.10. Its API surface may change in future releases without following semver.

Camunda API operations use dynamic variables and customHeaders payloads. By default these are untyped (object), but you can opt in to compile-time type safety using your own DTOs.

Sending Variables (Input)

Assign any DTO or dictionary to the Variables property — System.Text.Json serializes the runtime type automatically:

using Camunda.Orchestration.Sdk;

// Define your application domain models
public record OrderInput(string OrderId, decimal Amount);

// Assign the DTO directly
await client.CreateProcessInstanceAsync(new ProcessInstanceCreationInstructionById
{
    ProcessDefinitionId = ProcessDefinitionId.AssumeExists("order-process"),
    Variables = new OrderInput("ord-123", 99.99m),
});

// Dictionaries also work — no DTO required
await client.CompleteJobAsync(jobKey, new JobCompletionRequest
{
    Variables = new Dictionary<string, object> { ["processed"] = true },
});

Receiving Variables (Output)

Use DeserializeAs<T>() to extract typed DTOs from API responses:

using Camunda.Orchestration.Sdk;

public record OrderResult(bool Processed, string InvoiceNumber);

// Deserialize variables from any API response
var result = await client.CreateProcessInstanceAsync(
    new ProcessInstanceCreationInstructionById
    {
        ProcessDefinitionId = ProcessDefinitionId.AssumeExists("test"),
    });
var output = result.Variables.DeserializeAs<OrderResult>();
// output.Processed, output.InvoiceNumber — fully typed

DeserializeAs<T>() handles the common runtime shapes:

• JsonElement (standard API response) → deserialized via System.Text.Json
• Already the target type → returned as-is (zero-copy)
• null → returns default(T)

Custom JsonSerializerOptions can be passed for non-standard naming conventions.