我认为您应该使用“GUID”而不是“UniqueId”
查看此链接并找到这部分文档。
检索特定列表项
以下示例显示如何检索特定列表项。
HTTP 获取
https://{site_url}/_api/web/lists/GetByTitle('Test')/items({item_id})
Authorization: "Bearer " + accessToken
Accept: "application/json;odata=verbose"
以下 XML 显示了请求 XML 内容类型时返回的列表项属性的示例。
XML
<content type="application/xml">
<m:properties>
<d:FileSystemObjectType m:type="Edm.Int32">0</d:FileSystemObjectType>
<d:Id m:type="Edm.Int32">1</d:Id>
<d:ID m:type="Edm.Int32">1</d:ID>
<d:ContentTypeId>0x010049564F321A0F0543BA8C6303316C8C0F</d:ContentTypeId>
<d:Title>an item</d:Title>
<d:Modified m:type="Edm.DateTime">2012-07-24T22:47:26Z</d:Modified>
<d:Created m:type="Edm.DateTime">2012-07-24T22:47:26Z</d:Created>
<d:AuthorId m:type="Edm.Int32">11</d:AuthorId>
<d:EditorId m:type="Edm.Int32">11</d:EditorId>
<d:OData__UIVersionString>1.0</d:OData__UIVersionString>
<d:Attachments m:type="Edm.Boolean">false</d:Attachments>
<d:GUID m:type="Edm.Guid">eb6850c5-9a30-4636-b282-234eda8b1057</d:GUID>
</m:properties>
</content>
如您所见,返回值包含 GUID 标记