Dynamic content

Although the framework is build on the intend of providing type information as much as possible it can be necessary to deviate from this approach.

Dynamic Actions

(v4.2.0)

In certain scenarios an actions parameters (or not having any) is determined at runtime. This special case can be implemented using DynamicHypermediaAction. This action allows for a runtime dynamic schema to be retrieved. To decide what schema is desired it is required to pass runtime values to the schema routes. DynamicHypermediaAction has the property SchemaRouteKeys which accepts an object which will be passed to route generation so route keys can be filled with values. This also requires a custom route for the dynamic schemas using [HttpGetHypermediaActionParameterInfo]. For this to work the custom type route has to:

• have route keys which match the properties in SchemaRouteKeys so they can be filled.
• the type route is identified by a IHypermediaActionParameter used as marker to find the route.

Prefilled values can be provided as object which will be serialized and as string which has to contain a valid json object.

Example:

// Action route, retreiving raw json
[HttpPostHypermediaAction("/MyDynamicAction", typeof(MyDynamicOp))]
public ActionResult MyDynamicAction([FromBody] JsonElement rawObject)
{
    // check rawObject if it matches your dynamic schema if required
    ...
    return Ok();
}

// Dynamic schema route, will work next to default generated ones
[HttpGetHypermediaActionParameterInfo("MyGenericParametersType/{schemaKey1}/{schemaKey2}", typeof(MyGenericParameters))] 
public ActionResult MyGenericParametersType([FromRoute] string schemaKey1, [FromRoute] string schemaKey2)
{
    // dynamic keys passed to the action are passed here by build URL so the schema can be selected 
    var schema = GetMyDynamicSchema(schemaKey1, schemaKey2);
    return Content(schema, DefaultMediaTypes.ApplicationJson);
}

// Action definition for HTO
public class MyDynamicOp : DynamicHypermediaAction<GenericProcessingConfigureParameters>
{
    // accepts dynamic values relevant for schema selection
    public MyDynamicOp(string schemaKey1Value, string schemaKey2Value, bool hasParameters, object? prefilledValues = null) 
        : base(hasParameters, prefilledValues)
    {
        // property names have to match the route for MyGenericParameters type, will be used to build the URL
        SchemaRouteKeys = new {schemaKey1=schemaKey1Value, schemaKey2= schemaKey2Value};
    }
}

// only used as marker class so custom type route is selected
public class MyGenericParameters : IHypermediaActionParameter { }

// Usage in the HTO
...
// assign the configured action with runtime information
// create prefilled values, three options
var prefilledValues = "{...}" // JSON object as string
prefilledValues = myObject; // static object
prefilledValues = new {property=1}; // anonymous object

MyDynamicOp = new MyDynamicOp(schemaKey1Value, schemaKey2Value, currentActionHasParameters(), prefilledValues);