调用Microsoft Graph API获取SharePoint文件统计时遇JSON解析错误

问题场景 #

尝试通过以下代码获取SharePoint站点文件使用统计：

var report_SP_Usage_File_Counts = await 
graphClient.Reports.GetSharePointSiteUsageFileCounts("D180").Request().GetAsync();

执行后抛出JSON解析错误：

System.Text.Json.JsonException: 'R' is an invalid start of a value. Path: $ | LineNumber: 0 | BytePositionInLine: 0.
---> System.Text.Json.JsonReaderException: 'R' is an invalid start of a value. LineNumber: 0 | BytePositionInLine: 0.
  at System.Text.Json.ThrowHelper.ThrowJsonReaderException(Utf8JsonReader& json, ExceptionResource resource, Byte nextByte, ReadOnlySpan`1 bytes)
  at System.Text.Json.Utf8JsonReader.ConsumeValue(Byte marker)
  at System.Text.Json.Utf8JsonReader.ReadFirstToken(Byte first)
  at System.Text.Json.Utf8JsonReader.ReadSingleSegment()
  at System.Text.Json.Utf8JsonReader.Read()
  at System.Text.Json.Serialization.JsonConverter`1.ReadCore(Utf8JsonReader& reader, JsonSerializerOptions options, ReadStack& state)
--- End of inner exception stack trace ---
  at System.Text.Json.ThrowHelper.ReThrowWithPath(ReadStack& state, JsonReaderException ex)
  at System.Text.Json.Serialization.JsonConverter`1.ReadCore(Utf8JsonReader& reader, JsonSerializerOptions options, ReadStack& state)
  at System.Text.Json.JsonSerializer.ReadCore[TValue](JsonConverter jsonConverter, Utf8JsonReader& reader, JsonSerializerOptions options, ReadStack& state)
  at System.Text.Json.JsonSerializer.ReadCore[TValue](JsonReaderState& readerState, Boolean isFinalBlock, ReadOnlySpan`1 buffer, JsonSerializerOptions options, ReadStack& state, JsonConverter converterBase)
  at System.Text.Json.JsonSerializer.ContinueDeserialize[TValue](ReadBufferState& bufferState, JsonReaderState& jsonReaderState, ReadStack& readStack, JsonConverter converter, JsonSerializerOptions options)
  at System.Text.Json.JsonSerializer.ReadAllAsync[TValue](Stream utf8Json, JsonTypeInfo jsonTypeInfo, CancellationToken cancellationToken)
  at Microsoft.Graph.Serializer.DeserializeObject[T](Stream stream)
  at Microsoft.Graph.ResponseHandler.HandleResponse[T](HttpResponseMessage response)
  at Microsoft.Graph.BaseRequest.SendAsync[T](Object serializableObject, CancellationToken cancellationToken, HttpCompletionOption completionOption)
  at MinimalAPI.Endpoints.Reporting.mw_m365_GroupActivityTable_GRAPH()
  at Microsoft.AspNetCore.Http.RequestDelegateFactory.<ExecuteTask>g__ExecuteAwaited|58_0[T](Task`1 task, HttpContext httpContext)
  at Microsoft.AspNetCore.Routing.EndpointMiddleware.<Invoke>g__AwaitRequestTask|6_0(Endpoint endpoint, Task requestTask, ILogger logger)
  at Swashbuckle.AspNetCore.SwaggerUI.SwaggerUIMiddleware.Invoke(HttpContext httpContext)
  at Swashbuckle.AspNetCore.Swagger.SwaggerMiddleware.Invoke(HttpContext httpContext, ISwaggerProvider swaggerProvider)
  at Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware.Invoke(HttpContext context)

错误原因 #

Microsoft Graph的GetSharePointSiteUsageFileCountsAPI返回的是CSV格式数据，而非JSON。默认的Graph客户端尝试将返回内容反序列化为JSON对象，而CSV的开头字符（通常是表头的第一个字母，比如"Report Date"的'R'）不符合JSON格式，因此抛出解析错误。

正确实现步骤 #

1. 获取原始CSV内容：不使用强类型的GetAsync()，而是直接获取HTTP响应并读取CSV字符串。
2. 解析CSV数据：使用CSV解析库（如CsvHelper）将字符串转换为可操作的实体对象。

代码示例 #

1. 获取CSV内容

// 创建请求
var request = graphClient.Reports.GetSharePointSiteUsageFileCounts("D180").Request();
// 发送请求并获取响应
var response = await request.SendAsync(HttpCompletionOption.ResponseHeadersRead);
// 读取CSV字符串
var csvContent = await response.Content.ReadAsStringAsync();

2. 解析CSV（使用CsvHelper）

首先安装CsvHelper NuGet包：Install-Package CsvHelper

然后定义对应CSV列的实体类：

using CsvHelper.Configuration.Attributes;
using System.Globalization;

public class SharePointSiteUsageFileCount
{
    [Name("Report Date")]
    public DateTime ReportDate { get; set; }
    
    [Name("Site Type")]
    public string SiteType { get; set; }
    
    [Name("Total")]
    public long TotalFiles { get; set; }
    
    [Name("Active")]
    public long ActiveFiles { get; set; }
}

最后解析CSV：

using var stringReader = new StringReader(csvContent);
using var csvReader = new CsvHelper.CsvReader(stringReader, CultureInfo.InvariantCulture);
var usageRecords = csvReader.GetRecords<SharePointSiteUsageFileCount>().ToList();

必要权限 #

调用该API需要Reports.Read.All权限，可配置为：

• 应用权限：适用于后台服务场景
• 委派权限：需要用户拥有全局管理员、报表阅读器等角色

内容的提问来源于stack exchange，提问作者redoc01