How do I map a single .NET type to multiple nested object types in ElasticSearch/NEST?

If I understand correctly your intention, Entity object will have only nested objects in it, won't it?

You can try to use dynamic mapping functionality of elasticsearch for entity object. I assume Entity is a root object.

curl -X POST localhost:9200/myindex/entity/_mapping{"dynamic_templates": [    {"nested_data_template": {        "mapping": {            "type": "nested" },        "match_mapping_type": "object",        "path_match": "*" }}]}

path_match: * and match_mapping_type: object mean that for all field names with object as a value nested type mapping will be applied.

Using NEST and Fluent API you can use the following API. IntelliSense will guide you how to build mapping above. ;)

descriptor.DynamicTemplates(DynamicTemplatesDescriptor<Entity>)

Every time when a new property matching this template appears, elasticsearch will update mapping based on dynamic mapping. After a while your mapping will look like:

{  "entity": {    "mappings": {      "entity": {        "dynamic_templates": [          {            "nested_data_template": {              "mapping": {                "type": "nested"              },              "match_mapping_type": "object",              "path_match": "*"            }          }        ],        "properties": {          "test": {            "type": "nested",            "properties": {              "test": {                "type": "string"              },              "another_property": {                "type": "string"              }            }          },          "test1": {            "type": "nested",            "properties": {              "test": {                "type": "string"              }            }          }        }      }    }  }}

Hope this will help!