First of all, thanks for the answer GregKalapos.
Correct, not appears the connection. Do you want the stacktrace? If I copy all the document I reach to the max lenght of the message  This is the all the document without the stacktrace.
 This is the all the document without the stacktrace.
{
  "_index": "apm-7.8.0-span",
  "_type": "_doc",
  "_id": "vrv8dnMB42TIazIZksQH",
  "_version": 1,
  "_score": null,
  "_source": {
    "parent": {
      "id": "b4cd898682f5db4b"
    },
    "observer": {
      "hostname": "8cd8204852f1",
      "name": "instance-0000000000",
      "id": "a5e63c40-5d81-4957-b448-442e72dc0586",
      "ephemeral_id": "52b17444-d645-4894-8ec0-473b674935fd",
      "type": "apm-server",
      "version": "7.8.0",
      "version_major": 7
    },
    "agent": {
      "name": "dotnet",
      "version": "1.6.0"
    },
    "trace": {
      "id": "b4496a60d185b54c8d214495fcffd9c1"
    },
    "@timestamp": "2020-07-22T14:45:24.278Z",
    "ecs": {
      "version": "1.5.0"
    },
    "service": {
      "environment": "Development",
      "name": "MyApp"
    },
    "destination": {
      "address": "localhost",
      "port": 5010
    },
    "processor": {
      "name": "transaction",
      "event": "span"
    },
    "transaction": {
      "id": "b4cd898682f5db4b"
    },
    "timestamp": {
      "us": 1595429124278547
    },
    "span": {
      "duration": {
        "us": 478511
      },
"subtype": "http",
      "name": "GET localhost",
      "http": {
        "method": "get",
        "response": {
          "status_code": 200
        },
        "url": {
          "original": "http://localhost:5010/api/values/1"
        }
      },
      "id": "ec7a04be3ad09890",
      "type": "external"
    }
  },
  "fields": {
    "file.created": [],
    "process.parent.start": [],
    "event.end": [],
    "file.ctime": [],
    "tls.client.not_after": [],
    "event.ingested": [],
    "@timestamp": [
      "2020-07-22T14:45:24.278Z"
    ],
    "file.mtime": [],
    "event.created": [],
    "file.accessed": [],
    "tls.server.not_before": [],
    "package.installed": [],
    "tls.client.not_before": [],
    "event.start": [],
    "tls.server.not_after": [],
    "process.start": []
  },
  "highlight": {
    "trace.id": [
      "@kibana-highlighted-field@b4496a60d185b54c8d214495fcffd9c1@/kibana-highlighted-field@"
    ]
  },
  "sort": [
    1595429124278
  ]
}
Thanks!!