# Class AggregatingExternalParametersProvider

OptimaJet.Workflow.Core.Runtime.AggregatingExternalParametersProvider

Combines registered [IWorkflowExternalParametersProvider](https://api.workflowengine.io/core/OptimaJet.Workflow.Core.Runtime/IWorkflowExternalParametersProvider/) implementations into one provider and routes external parameter operations by parameter ownership and access mode.

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

```csharp
public class AggregatingExternalParametersProvider : BaseAggregatingProvider<IWorkflowExternalParametersProvider>, IWorkflowExternalParametersProvider
```

## Type Hierarchy

-   [BaseAggregatingProvider<IWorkflowExternalParametersProvider>](https://api.workflowengine.io/core/OptimaJet.Workflow.Core.Runtime/BaseAggregatingProvider-T/)
    -   AggregatingExternalParametersProvider Current type
        -   Implemented interfaces
            -   [IWorkflowExternalParametersProvider](https://api.workflowengine.io/core/OptimaJet.Workflow.Core.Runtime/IWorkflowExternalParametersProvider/)

## Methods

`public Task<object> GetExternalParameterAsync(string parameterName, ProcessInstance processInstance)` 

Gets the value of the named external parameter asynchronously.

### Parameters

| Name | Type | Description |
| --- | --- | --- |
| `parameterName` | `String` | The external parameter name. |
| `processInstance` | `ProcessInstance` | The workflow process instance for which the parameter is requested. |

### Returns

| Type | Description |
| --- | --- |
| `Task<Object>` | The asynchronous result containing the external parameter value. |

### Exceptions

| Type | Description |
| --- | --- |
| `NotImplementedException` | Thrown synchronously when no applicable provider both recognizes the parameter and reports asynchronous reads. |

### Remarks

The runtime calls this method when [IWorkflowExternalParametersProvider.IsGetExternalParameterAsync(string, string, ProcessInstance)](https://api.workflowengine.io/core/OptimaJet.Workflow.Core.Runtime/IWorkflowExternalParametersProvider/) is [true](https://learn.microsoft.com/dotnet/csharp/language-reference/builtin-types/bool) for the same parameter and scheme combination.

`public object GetExternalParameter(string parameterName, ProcessInstance processInstance)` 

Gets the value of the named external parameter synchronously.

### Parameters

| Name | Type | Description |
| --- | --- | --- |
| `parameterName` | `String` | The external parameter name. |
| `processInstance` | `ProcessInstance` | The workflow process instance for which the parameter is requested. |

### Returns

| Type | Description |
| --- | --- |
| `Object` | The external parameter value. |

### Exceptions

| Type | Description |
| --- | --- |
| `NotImplementedException` | Thrown when no applicable provider both recognizes the parameter and reports synchronous reads. |

### Remarks

The runtime calls this method when [IWorkflowExternalParametersProvider.IsGetExternalParameterAsync(string, string, ProcessInstance)](https://api.workflowengine.io/core/OptimaJet.Workflow.Core.Runtime/IWorkflowExternalParametersProvider/) is [false](https://learn.microsoft.com/dotnet/csharp/language-reference/builtin-types/bool) for the same parameter and scheme combination.

`public Task SetExternalParameterAsync(string parameterName, object parameterValue, ProcessInstance processInstance)` 

Writes the named external parameter value asynchronously.

### Parameters

| Name | Type | Description |
| --- | --- | --- |
| `parameterName` | `String` | The external parameter name. |
| `parameterValue` | `Object` | The value to write. |
| `processInstance` | `ProcessInstance` | The workflow process instance for which the parameter is updated. |

### Returns

| Type | Description |
| --- | --- |
| `Task` | A task that completes when the parameter value is written. |

### Exceptions

| Type | Description |
| --- | --- |
| `NotImplementedException` | Thrown synchronously when no applicable provider both recognizes the parameter and reports asynchronous writes. |

### Remarks

The runtime calls this method when [IWorkflowExternalParametersProvider.IsSetExternalParameterAsync(string, string, ProcessInstance)](https://api.workflowengine.io/core/OptimaJet.Workflow.Core.Runtime/IWorkflowExternalParametersProvider/) is [true](https://learn.microsoft.com/dotnet/csharp/language-reference/builtin-types/bool) for the same parameter and scheme combination.

`public void SetExternalParameter(string parameterName, object parameterValue, ProcessInstance processInstance)` 

Writes the named external parameter value synchronously.

### Parameters

| Name | Type | Description |
| --- | --- | --- |
| `parameterName` | `String` | The external parameter name. |
| `parameterValue` | `Object` | The value to write. |
| `processInstance` | `ProcessInstance` | The workflow process instance for which the parameter is updated. |

### Exceptions

| Type | Description |
| --- | --- |
| `NotImplementedException` | Thrown when no applicable provider both recognizes the parameter and reports synchronous writes. |

### Remarks

The runtime calls this method when [IWorkflowExternalParametersProvider.IsSetExternalParameterAsync(string, string, ProcessInstance)](https://api.workflowengine.io/core/OptimaJet.Workflow.Core.Runtime/IWorkflowExternalParametersProvider/) is [false](https://learn.microsoft.com/dotnet/csharp/language-reference/builtin-types/bool) for the same parameter and scheme combination.

`public bool IsGetExternalParameterAsync(string parameterName, string schemeCode, ProcessInstance processInstance)` 

Checks whether asynchronous external-parameter reads are supported for the named parameter.

### Parameters

| Name | Type | Description |
| --- | --- | --- |
| `parameterName` | `String` | The external parameter name. |
| `schemeCode` | `String` | The scheme code for provider selection. |
| `processInstance` | `ProcessInstance` | The workflow process instance used for context checks. |

### Returns

| Type | Description |
| --- | --- |
| `Boolean` | [true](https://learn.microsoft.com/dotnet/csharp/language-reference/builtin-types/bool) if [IWorkflowExternalParametersProvider.GetExternalParameterAsync(string, ProcessInstance)](https://api.workflowengine.io/core/OptimaJet.Workflow.Core.Runtime/IWorkflowExternalParametersProvider/) is supported. |

### Remarks

Providers are queried from most recently registered to earliest until one returns [true](https://learn.microsoft.com/dotnet/csharp/language-reference/builtin-types/bool). This method does not call [IWorkflowExternalParametersProvider.HasExternalParameter(string, string, ProcessInstance)](https://api.workflowengine.io/core/OptimaJet.Workflow.Core.Runtime/IWorkflowExternalParametersProvider/).

`public bool IsSetExternalParameterAsync(string parameterName, string schemeCode, ProcessInstance processInstance)` 

Checks whether asynchronous external-parameter writes are supported for the named parameter.

### Parameters

| Name | Type | Description |
| --- | --- | --- |
| `parameterName` | `String` | The external parameter name. |
| `schemeCode` | `String` | The scheme code for provider selection. |
| `processInstance` | `ProcessInstance` | The workflow process instance used for context checks. |

### Returns

| Type | Description |
| --- | --- |
| `Boolean` | [true](https://learn.microsoft.com/dotnet/csharp/language-reference/builtin-types/bool) if [IWorkflowExternalParametersProvider.SetExternalParameterAsync(string, object, ProcessInstance)](https://api.workflowengine.io/core/OptimaJet.Workflow.Core.Runtime/IWorkflowExternalParametersProvider/) is supported. |

### Remarks

Providers are queried from most recently registered to earliest until one returns [true](https://learn.microsoft.com/dotnet/csharp/language-reference/builtin-types/bool). This method does not call [IWorkflowExternalParametersProvider.HasExternalParameter(string, string, ProcessInstance)](https://api.workflowengine.io/core/OptimaJet.Workflow.Core.Runtime/IWorkflowExternalParametersProvider/).

`public bool HasExternalParameter(string parameterName, string schemeCode, ProcessInstance processInstance)` 

Checks whether the named external parameter exists in this provider for the scheme and process context.

### Parameters

| Name | Type | Description |
| --- | --- | --- |
| `parameterName` | `String` | The external parameter name. |
| `schemeCode` | `String` | The scheme code for provider selection. |
| `processInstance` | `ProcessInstance` | The workflow process instance used for context checks. |

### Returns

| Type | Description |
| --- | --- |
| `Boolean` | [true](https://learn.microsoft.com/dotnet/csharp/language-reference/builtin-types/bool) if the parameter is recognized by the provider. |

### Remarks

Providers are queried from most recently registered to earliest until one returns [true](https://learn.microsoft.com/dotnet/csharp/language-reference/builtin-types/bool).

## Remarks

For a scheme, both global providers and providers registered specifically for that scheme are applicable. Providers are searched from the most recently registered to the earliest, regardless of registration scope. A read or write is forwarded to the first provider that recognizes the parameter and whose synchronous or asynchronous mode matches the method being called. Providers with a different access mode are skipped.

[AggregatingExternalParametersProvider.HasExternalParameter(string, string, ProcessInstance)](https://api.workflowengine.io/core/OptimaJet.Workflow.Core.Runtime/AggregatingExternalParametersProvider/), [AggregatingExternalParametersProvider.IsGetExternalParameterAsync(string, string, ProcessInstance)](https://api.workflowengine.io/core/OptimaJet.Workflow.Core.Runtime/AggregatingExternalParametersProvider/), and [AggregatingExternalParametersProvider.IsSetExternalParameterAsync(string, string, ProcessInstance)](https://api.workflowengine.io/core/OptimaJet.Workflow.Core.Runtime/AggregatingExternalParametersProvider/) are aggregate queries: each returns [true](https://learn.microsoft.com/dotnet/csharp/language-reference/builtin-types/bool) when any applicable provider returns [true](https://learn.microsoft.com/dotnet/csharp/language-reference/builtin-types/bool). The asynchronous-mode queries do not first require the same provider to report that it recognizes the parameter.

[Previous AggregatingDesignerParameterFormatProvider](https://api.workflowengine.io/core/OptimaJet.Workflow.Core.Runtime/AggregatingDesignerParameterFormatProvider/) [Next AggregatingRuleProvider](https://api.workflowengine.io/core/OptimaJet.Workflow.Core.Runtime/AggregatingRuleProvider/)