NJsonSchema生成C#代码时生成泛型对象而非指定类的问题

问题场景 #

使用NJsonSchema处理一份第三方定义、无法修改的JSON Schema，需要生成能输出符合该Schema的C#类，但工具仅生成了泛型object类型的字典，未生成Schema中定义的具体字段和强类型类。

生成器代码 #

var schema = JsonSchema.FromFileAsync(@"../../../SchemaSnippets.json");
CSharpGeneratorSettings set = new CSharpGeneratorSettings();
set.Namespace = "EPJSON";
set.SchemaType = SchemaType.JsonSchema;
set.GenerateDataAnnotations = true;
set.AnyType = "object";
set.ClassStyle = CSharpClassStyle.Poco;
set.HandleReferences = false;
var generator = new CSharpGenerator(schema.Result, set);
var file = generator.GenerateFile();
File.WriteAllText(@"../../../SchemaSnippetsCode.cs", file);

目标Schema片段 #

{
  "$schema": "https://json-schema.org/draft-07/schema#",
  "properties": {
    "Version": {
      "patternProperties": {
        ".*": {
          "type": "object",
          "properties": {
            "version_identifier": {
              "type": "string",
              "default": "22.2"
            }
          }
        }
      },
      "group": "Simulation Parameters",
      "legacy_idd": {
        "field_info": {
          "version_identifier": {
            "field_name": "Version Identifier",
            "field_type": "a"
          }
        },
        "fields": [
          "version_identifier"
        ],
        "alphas": {
          "fields": [
            "version_identifier"
          ]
        },
        "numerics": {
          "fields": []
        }
      },
      "type": "object",
      "maxProperties": 1,
      "memo": "Specifies the EnergyPlus version of the IDF file.",
      "format": "singleLine"
    }
  }
}

当前生成的C#代码 #

[System.CodeDom.Compiler.GeneratedCode("NJsonSchema", "10.8.0.0 (Newtonsoft.Json v9.0.0.0)")]
[Newtonsoft.Json.JsonProperty("Version", Required = Newtonsoft.Json.Required.DisallowNull, NullValueHandling = Newtonsoft.Json.NullValueHandling.Ignore)]
public System.Collections.Generic.IDictionary<string, object> Version { get; set; }
private System.Collections.Generic.IDictionary<string, object> _additionalProperties;
[Newtonsoft.Json.JsonExtensionData]
public System.Collections.Generic.IDictionary<string, object> AdditionalProperties
{
    get { return _additionalProperties ?? (_additionalProperties = new System.Collections.Generic.Dictionary<string, object>()); }
    set { _additionalProperties = value; }
}

期望生成的C#代码 #

public System.Collections.Generic.IDictionary<string, VersionObject> Version { get; set; }

class VersionObject
{
    string version_identifier { get; set; } = "22.2";
}

解决方案 #

1. 启用PatternProperties类生成选项 #

NJsonSchema默认不会为patternProperties中的子结构生成强类型类，需要在生成器设置中开启GeneratePatternPropertiesAsClasses选项：

var set = new CSharpGeneratorSettings();
set.Namespace = "EPJSON";
set.SchemaType = SchemaType.JsonSchema;
set.GenerateDataAnnotations = true;
set.AnyType = "object";
set.ClassStyle = CSharpClassStyle.Poco;
set.HandleReferences = false;
// 关键配置：开启patternProperties的强类型类生成
set.GeneratePatternPropertiesAsClasses = true;

2. 升级NJsonSchema版本（可选） #

你当前使用的是10.8.0版本，该版本对patternProperties的支持可能存在局限性。建议升级到最新稳定版，能更好地处理这类动态键的Schema结构。

效果验证 #

修改配置后重新生成，NJsonSchema会为patternProperties中匹配任意键的子对象生成对应的VersionObject类，并将Version属性的字典类型改为IDictionary<string, VersionObject>，与你期望的代码结构一致。

内容的提问来源于stack exchange，提问作者timkado