# Interface IExternalExpressionsCompiler

OptimaJet.Workflow.Core.CodeActions.IExternalExpressionsCompiler

Compiles a workflow expression into an asynchronous function.

Namespace: [OptimaJet.Workflow.Core.CodeActions](https://api.workflowengine.io/core/OptimaJet.Workflow.Core.CodeActions/)

```csharp
public interface IExternalExpressionsCompiler
```

## Methods

`Func<ProcessInstance, Task<TResult>> Compile<TResult>(ExpressionCompilationRequest request)` 

Compiles the expressions in the request without reading process values.

### Parameters

| Name | Type | Description |
| --- | --- | --- |
| `request` | `ExpressionCompilationRequest` | Source expressions, their prepared form, and compilation context. |

### Returns

| Type | Description |
| --- | --- |
| `Func<ProcessInstance, Task<TResult>>` | A non-null function that receives the current process instance on each call. |

## Remarks

Core can call Compile concurrently. Implementations must not execute the returned function during compilation. Throw an exception to reject an expression. Core does not retry with the built-in compiler or use the text as a literal. This interface does not isolate code or limit its execution.

[Previous IExternalCompiler](https://api.workflowengine.io/core/OptimaJet.Workflow.Core.CodeActions/IExternalCompiler/) [Next RegexPattern](https://api.workflowengine.io/core/OptimaJet.Workflow.Core.CodeActions/RegexPattern/)