C# Azure Functions中OkObjectResult未返回JSON仅返回对象类型名问题

当前接口返回类型名而非对象JSON结构的核心原因有两个：

1. 直接使用字符串插值$"Successfully executed {accessabilityResult}"拼接对象时，C#会默认调用对象的ToString()方法，由于AccessibilityErrorOutput类没有重写ToString()方法，默认返回对象的全限定类型名。
2. 接口OpenApi配置标注返回类型为text/plain纯文本，运行时不会对传入内容做对象JSON序列化处理。

• 修改OpenApi响应特性配置，将响应内容类型改为application/json，匹配JSON返回格式。
• 构造包含提示文本和结果对象的复合响应载体，传入OkObjectResult，Functions运行时会自动将整个对象序列化为标准JSON结构返回。

public class AccCheckerForOpenXML
{
    private readonly ILogger<AccCheckerForOpenXML> logger;
    public AccCheckerForOpenXML(ILogger<AccCheckerForOpenXML> log) => this.logger = log;
    /// <summary>
    /// Function that receives a httptrigger and then starts processing documents the Office Open XML files.
    /// </summary>
    [FunctionName("AccCheckerForOpenXML")]
    [OpenApiOperation(operationId: "Run", tags: new[] { "docName" })]
    [OpenApiParameter(name: "name", In = ParameterLocation.Query, Required = true, Type = typeof(string), Description = "The **Name** parameter")]
    // 修改响应配置：contentType改为application/json，bodyType改为object
    [OpenApiResponseWithBody(statusCode: HttpStatusCode.OK, contentType: "application/json", bodyType: typeof(object), Description = "The OK response")]
    public async Task<IActionResult> Run(
            [HttpTrigger(AuthorizationLevel.Anonymous, "get", "post", Route = null)] HttpRequest req)
    {
        this.logger.LogInformation("AccCheckerForDocx: Run method:HTTP trigger --  function processed a request.");
        string filePath = req.Query["name"];
        var requestBody = await new StreamReader(req.Body).ReadToEndAsync();
        dynamic data = JsonConvert.DeserializeObject(requestBody);
        filePath ??= data?.name;
        

        // Http Response
        if (filePath == null)
        {
            return new BadRequestObjectResult("Did not execute. Please include the file path");
        }

        else
        {
            var accessabilityResult = await DocumentProcessor.ProcessDocumentMainAsync(filePath, this.logger);
            // 返回匿名对象作为响应载体，包含提示信息和结果数据
            return new OkObjectResult(new 
            {
                Message = "Successfully executed",
                Data = accessabilityResult
            });
        }

    }
}

接口正常返回200状态码，响应内容为标准JSON格式，结构如下：

{
  "Message": "Successfully executed",
  "Data": {
    // 此处为accessabilityResult对象所有属性序列化后的内容
  }
}

如果你有特殊需求必须返回纯文本格式而非JSON结构，可以手动序列化accessabilityResult后再拼接字符串：

string resultJson = JsonConvert.SerializeObject(accessabilityResult);
return new OkObjectResult($"Successfully executed\n{resultJson}");

但这种方式不符合REST接口规范，客户端解析成本更高，优先推荐返回结构化JSON的方案。

内容的提问来源于stack exchange，提问作者Coco