# Class ParameterDefinition

OptimaJet.Workflow.Core.Model.ParameterDefinition

Defines a process parameter declared in [ProcessDefinition.Parameters](https://api.workflowengine.io/core/OptimaJet.Workflow.Core.Model/ProcessDefinition/).

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

```csharp
public class ParameterDefinition : BaseDefinition
```

## Type Hierarchy

-   [BaseDefinition](https://api.workflowengine.io/core/OptimaJet.Workflow.Core.Model/BaseDefinition/)
    -   ParameterDefinition Current type
        -   [ParameterDefinitionWithValue](https://api.workflowengine.io/core/OptimaJet.Workflow.Core.Model/ParameterDefinitionWithValue/)

## Properties

`[JsonConverter(typeof(NewtonsoftStringTypeConverter))] [JsonConverter(typeof(SystemTextStringTypeConverter))] public virtual Type Type { get; set; }` 

Gets or sets the CLR [Type](https://learn.microsoft.com/dotnet/api/system.type) used for process parameter values.

`[JsonConverter(typeof(StringEnumConverter))] [JsonConverter(typeof(SystemStringEnumConverter<ParameterPurpose>))] public virtual ParameterPurpose Purpose { get; set; }` 

Gets or sets the [ParameterPurpose](https://api.workflowengine.io/core/OptimaJet.Workflow.Core.Model/ParameterPurpose/) that controls how Workflow Engine manages and stores the process parameter.

`public virtual string InitialValue { get; set; }` 

Gets or sets the stored representation of the process parameter's initial value. Workflow Engine uses this value when initializing a parameter whose [ParameterDefinition.Purpose](https://api.workflowengine.io/core/OptimaJet.Workflow.Core.Model/ParameterDefinition/) is [ParameterPurpose.Persistence](https://api.workflowengine.io/core/OptimaJet.Workflow.Core.Model/ParameterPurpose/).

## Methods

`public static ParameterDefinition Create(string name, Type type, ParameterPurpose purpose, string initialValue = null)` 

Creates a [ParameterDefinition](https://api.workflowengine.io/core/OptimaJet.Workflow.Core.Model/ParameterDefinition/) with the specified settings.

### Parameters

| Name | Type | Description |
| --- | --- | --- |
| `name` | `String` | The process parameter name. |
| `type` | `Type` | The CLR [Type](https://learn.microsoft.com/dotnet/api/system.type) to assign to [ParameterDefinition.Type](https://api.workflowengine.io/core/OptimaJet.Workflow.Core.Model/ParameterDefinition/). |
| `purpose` | `ParameterPurpose` | The [ParameterPurpose](https://api.workflowengine.io/core/OptimaJet.Workflow.Core.Model/ParameterPurpose/) to assign to [ParameterDefinition.Purpose](https://api.workflowengine.io/core/OptimaJet.Workflow.Core.Model/ParameterDefinition/). |
| `initialValue` | `String` | The stored representation to assign to [ParameterDefinition.InitialValue](https://api.workflowengine.io/core/OptimaJet.Workflow.Core.Model/ParameterDefinition/), or [null](https://learn.microsoft.com/dotnet/csharp/language-reference/keywords/null) if no initial value is specified. |

### Returns

| Type | Description |
| --- | --- |
| `ParameterDefinition` | A new [ParameterDefinition](https://api.workflowengine.io/core/OptimaJet.Workflow.Core.Model/ParameterDefinition/) initialized with the specified settings. |

`public static ParameterDefinitionWithValue Create(ParameterDefinition parameterDefinition, object value)` 

Creates a [ParameterDefinitionWithValue](https://api.workflowengine.io/core/OptimaJet.Workflow.Core.Model/ParameterDefinitionWithValue/) by associating a value with a parameter definition.

### Parameters

| Name | Type | Description |
| --- | --- | --- |
| `parameterDefinition` | `ParameterDefinition` | The [ParameterDefinition](https://api.workflowengine.io/core/OptimaJet.Workflow.Core.Model/ParameterDefinition/) that describes the parameter. |
| `value` | `Object` | The current value to associate with `parameterDefinition`. |

### Returns

| Type | Description |
| --- | --- |
| `ParameterDefinitionWithValue` | A [ParameterDefinitionWithValue](https://api.workflowengine.io/core/OptimaJet.Workflow.Core.Model/ParameterDefinitionWithValue/) containing the parameter definition and the resulting value. |

### Exceptions

| Type | Description |
| --- | --- |
| `InvalidParameterValueException` | `value` is not assignable to [ParameterDefinition.Type](https://api.workflowengine.io/core/OptimaJet.Workflow.Core.Model/ParameterDefinition/) and cannot be converted to that type by [Convert.ChangeType(object, Type)](https://learn.microsoft.com/dotnet/api/system.convert.changetype#system-convert-changetype\(system-object-system-type\)). |

### Remarks

Unless [ParameterDefinition.Type](https://api.workflowengine.io/core/OptimaJet.Workflow.Core.Model/ParameterDefinition/) is [UnknownParameterType](https://api.workflowengine.io/core/OptimaJet.Workflow.Core.Model/UnknownParameterType/), the method passes a non-[null](https://learn.microsoft.com/dotnet/csharp/language-reference/keywords/null) `value` that is not assignable to the declared type to [Convert.ChangeType(object, Type)](https://learn.microsoft.com/dotnet/api/system.convert.changetype#system-convert-changetype\(system-object-system-type\)). When [ParameterDefinition.Purpose](https://api.workflowengine.io/core/OptimaJet.Workflow.Core.Model/ParameterDefinition/) is [ParameterPurpose.System](https://api.workflowengine.io/core/OptimaJet.Workflow.Core.Model/ParameterPurpose/), the returned object reuses `parameterDefinition`; otherwise, it contains the result of [ParameterDefinition.Clone()](https://api.workflowengine.io/core/OptimaJet.Workflow.Core.Model/ParameterDefinition/).

`public static ParameterDefinitionWithValue CreateFromPersistence(ParameterDefinition parameterDefinition, object value)` 

Creates a [ParameterDefinitionWithValue](https://api.workflowengine.io/core/OptimaJet.Workflow.Core.Model/ParameterDefinitionWithValue/) for a value loaded from persistence. The returned parameter is marked as unmodified and as already existing in the persistence store.

### Parameters

| Name | Type | Description |
| --- | --- | --- |
| `parameterDefinition` | `ParameterDefinition` | The [ParameterDefinition](https://api.workflowengine.io/core/OptimaJet.Workflow.Core.Model/ParameterDefinition/) that describes the persisted parameter. |
| `value` | `Object` | The value loaded from the persistence store. |

### Returns

| Type | Description |
| --- | --- |
| `ParameterDefinitionWithValue` | A [ParameterDefinitionWithValue](https://api.workflowengine.io/core/OptimaJet.Workflow.Core.Model/ParameterDefinitionWithValue/) containing the persisted value and its definition. |

### Exceptions

| Type | Description |
| --- | --- |
| `InvalidParameterValueException` | `value` is not assignable to [ParameterDefinition.Type](https://api.workflowengine.io/core/OptimaJet.Workflow.Core.Model/ParameterDefinition/) and cannot be converted to that type by [Convert.ChangeType(object, Type)](https://learn.microsoft.com/dotnet/api/system.convert.changetype#system-convert-changetype\(system-object-system-type\)). |

`public ParameterDefinition Clone()` 

Creates a copy of the current [ParameterDefinition](https://api.workflowengine.io/core/OptimaJet.Workflow.Core.Model/ParameterDefinition/).

### Returns

| Type | Description |
| --- | --- |
| `ParameterDefinition` | A copy of the current [ParameterDefinition](https://api.workflowengine.io/core/OptimaJet.Workflow.Core.Model/ParameterDefinition/). |

### Exceptions

| Type | Description |
| --- | --- |
| `NullReferenceException` | [BaseDefinition.DesignerSettings](https://api.workflowengine.io/core/OptimaJet.Workflow.Core.Model/BaseDefinition/) is [null](https://learn.microsoft.com/dotnet/csharp/language-reference/keywords/null). |

### Remarks

The operation uses [BaseDefinition.Clone()](https://api.workflowengine.io/core/OptimaJet.Workflow.Core.Model/BaseDefinition/) and therefore performs a shallow copy except for [BaseDefinition.DesignerSettings](https://api.workflowengine.io/core/OptimaJet.Workflow.Core.Model/BaseDefinition/).

## Remarks

The system parameter definitions exposed through [DefaultDefinitions.DefaultParameters](https://api.workflowengine.io/core/OptimaJet.Workflow.Core.Model/DefaultDefinitions/) ignore assignments to [ParameterDefinition.Type](https://api.workflowengine.io/core/OptimaJet.Workflow.Core.Model/ParameterDefinition/), [ParameterDefinition.Purpose](https://api.workflowengine.io/core/OptimaJet.Workflow.Core.Model/ParameterDefinition/), and [ParameterDefinition.InitialValue](https://api.workflowengine.io/core/OptimaJet.Workflow.Core.Model/ParameterDefinition/) after they are initialized.

[Previous PagedResponse<T>](https://api.workflowengine.io/core/OptimaJet.Workflow.Core.Model/PagedResponse-T/) [Next ParameterDefinitionReference](https://api.workflowengine.io/core/OptimaJet.Workflow.Core.Model/ParameterDefinitionReference/)