[英]EF Core Entity Post Error with entity that has other entities as properties
情況:
Executed 'ActivitysPost' (Failed, Id=a2e8a556-7b1b-4d0d-995c-65b9c494c802, Duration=26938ms)
[2021-05-03T05:04:29.141Z] System.Private.CoreLib: Exception while executing function: ActivitysPost.
Microsoft.EntityFrameworkCore.Relational: An error occurred while updating the entries.
See the inner exception for details.
Core .Net SqlClient Data Provider:
Cannot insert explicit value for identity column in table 'Helpers'
... when IDENTITY_INSERT is set to OFF.
錯誤發生在第 2 行:
_context.Add(activity);
await _context.SaveChangesAsync();
使用 EF Core 3.1.14
GitHub 項目(參見 API): https://github.com/djaus2/mslearn-staticwebsite-3entities
注意:以下確實有效(即提交新的助手和回合):
curl --header "Content-Type: application/json" --request POST --data "{'Name':'Recording','Quantity':1,'Round':{'No':1,'Description':'AVSL'},'Helper':{'Name':'FreedyFeelgood','Description':'BlaBlah'}}" http://localhost:7071/api/activitys/
返回結果:
{"id":6,"name":"Recording","quantity":1,"helper":{"id":13,"name":"FreedyFeelgood","description":"BlaBlah"},"round":{"id":7,"no":1,"description":"AVSL"}}
好的,所以查看代碼,您遇到的問題是 ef 無法識別作為已在數據庫中的實體附加的助手(和回合),而是將它們視為需要創建的新實體。
您可以通過附加從 api 調用反序列化的 Round 和 Helper 來解決此問題。
[FunctionName("ActivitysPost")]
public async Task<IActionResult> Run(
[HttpTrigger(AuthorizationLevel.Anonymous, "post", Route = "activitys")] HttpRequest req,
ILogger log)
{
var body = await new StreamReader(req.Body).ReadToEndAsync();
var activity = JsonConvert.DeserializeObject<Activity>(body);
....
_context.Attach(activity.Helper); // <-- new
_context.Attach(activity.Round); // <-- new
await _context.SaveChangesAsync();
return new OkObjectResult(activity);
}
這告訴 ef 假設它們來自數據庫,因此您不需要創建它們。 PUT 方法也會有同樣的問題,所以要小心。
希望這可以解決您的問題。
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