使用RestSharp调用SharePoint API创建文件夹时遇BadRequest错误

问题描述 #

基于.NET 6开发控制台应用，使用RestSharp调用SharePoint REST API创建文件夹时，收到BadRequest响应，错误信息：

"The property '__metadata' does not exist on type 'SP.Folder'. Make sure to only use property names that are defined by the type"

已在请求头指定Accept和Content-Type为application/json;odata=verbose，但问题仍未解决。

问题根源 #

RestSharp的AddJsonBody方法会自动覆盖请求的Content-Type头为application/json，而非你手动设置的application/json;odata=verbose。这导致SharePoint API未按OData Verbose模式解析请求体，因此无法识别__metadata属性。

解决方案 #

放弃使用AddJsonBody，改为手动序列化请求体为JSON字符串，并通过AddParameter方法指定正确的内容类型：

修改后的代码 #

using System.Text.Json;

// ... 其他代码 ...

var request = new RestRequest
{
    Resource = $"{RESOURCE}/_api/web/folders",
    Method = Method.Post
};

request.AddHeaders(new List<KeyValuePair<string, string>>
{
    new KeyValuePair<string, string>("Authorization", $"Bearer {_accessToken}"),
    new KeyValuePair<string, string>("Accept", "application/json;odata=verbose"),
    new KeyValuePair<string, string>("Content-Type", "application/json;odata=verbose")
});

// 手动序列化请求体
var folderPayload = new
{
    __metadata = new
    {
        type = "SP.Folder"
    },
    ServerRelativeUrl = $"ContainedFolder/{FolderName}"
};
var jsonPayload = JsonSerializer.Serialize(folderPayload);

// 添加请求体并指定正确的内容类型
request.AddParameter("application/json;odata=verbose", jsonPayload, ParameterType.RequestBody);

var response = await _client.ExecuteAsync(request);

if (response == null || response.StatusCode != expectedStatus)
    throw new Exception($"Unable to create folder. StatusCode: {response?.StatusCode}. Error: {response?.ErrorMessage}. RawContent: {response?.Content}");

return response;

额外检查点 #

• 确认RESOURCE为SharePoint站点的完整根URL（例如https://yourtenant.sharepoint.com/sites/yoursite）
• 确认ServerRelativeUrl是正确的服务器相对路径，需包含站点路径（例如站点为/sites/yoursite时，路径应为/sites/yoursite/ContainedFolder/{FolderName}）

内容的提问来源于stack exchange，提问作者Johan Pino