问题描述
我正在尝试将数据从json文件播种到数据库中,但是我一直遇到相同的错误。如下所示在堆栈跟踪中。我有一个AppQuestion类和一个IncorrectAnswer类。数据旨在匹配这些模型并传递到我的数据库中。尝试反序列化时,似乎种子不正确数组导致了错误。我宁愿使用System.Text.Json而不是Newsoft。有没有一种方法可以处理数据并忠实于我的模型。
SeedData.json:
[
{
"Question": "Question1","Incorrect": ["Answer1","Answer2","Answer3"],"Correct": "Answer4"
},{
"Question": "Question2","Answer4"],"Correct": "Answer3"
}
]
C#代码
public class Seed
{
public static async Task SeedQuestions(DataContext context)
{
if (await context.Questions.AnyAsync()) return;
var questionData = await System.IO.File.ReadAllTextAsync("Data/QuestionSeedData.json");
var questions = JsonSerializer.Deserialize<List<AppQuestion>>(questionData);
foreach(var question in questions)
{
context.Questions.Add(question);
}
await context.SaveChangesAsync();
}
}
public class AppQuestion
{
public int Id { get; set; }
public string Question { get; set; }
public ICollection<IncorrectAnswer> Incorrect { get; set; }
public string Correct { get; set; }
}
public class IncorrectAnswer
{
public int Id { get; set; }
public string Incorrect { get; set; }
public AppQuestion AppQuestion { get; set; }
public int AppQuestionId { get; set; }
}
public class DataContext : DbContext
{
public DataContext( DbContextOptions options) : base(options)
{
}
public DbSet<AppQuestion> Questions {get; set;}
public DbSet<AppUser> Users { get; set; }
}
public class Program
{
public static async Task Main(string[] args)
{
var host = CreateHostBuilder(args).Build();
using var scope = host.Services.CreateScope();
var services = scope.ServiceProvider;
try
{
var context = services.GetrequiredService<DataContext>();
await context.Database.MigrateAsync();
await Seed.SeedQuestions(context);
}
catch (Exception ex)
{
var logger = services.GetrequiredService<ILogger<Program>>();
logger.LogError(ex,"An error occurred during migration");
}
await host.RunAsync();
}
public static IHostBuilder CreateHostBuilder(string[] args) =>
Host.CreateDefaultBuilder(args)
.ConfigureWebHostDefaults(webBuilder =>
{
webBuilder.UseStartup<Startup>();
});
}
堆栈跟踪:
fail: API.Program[0]
An error occurred during migration
System.Text.Json.JsonException: The JSON value Could not be converted to API.Entities.IncorrectAnswer. Path: $[0].Incorrect[0] | LineNumber: 3 | BytePositionInLine: 28.
at System.Text.Json.ThrowHelper.ThrowJsonException_DeserializeUnabletoConvertValue(Type propertyType)
at System.Text.Json.Serialization.Converters.ObjectDefaultConverter`1.OnTryRead(Utf8JsonReader& reader,Type typetoConvert,JsonSerializerOptions options,ReadStack& state,T& value)
at System.Text.Json.Serialization.JsonConverter`1.TryRead(Utf8JsonReader& reader,T& value)
at System.Text.Json.Serialization.Converters.IEnumerableDefaultConverter`2.OnTryRead(Utf8JsonReader& reader,TCollection& value)
at System.Text.Json.Serialization.JsonConverter`1.TryRead(Utf8JsonReader& reader,T& value)
at System.Text.Json.JsonPropertyInfo`1.ReadJsonAndSetMember(Object obj,Utf8JsonReader& reader)
at System.Text.Json.Serialization.Converters.ObjectDefaultConverter`1.OnTryRead(Utf8JsonReader& reader,T& value)
at System.Text.Json.Serialization.JsonConverter`1.ReadCore(Utf8JsonReader& reader,ReadStack& state)
at System.Text.Json.JsonSerializer.ReadCore[TValue](JsonConverter jsonConverter,Utf8JsonReader& reader,ReadStack& state)
at System.Text.Json.JsonSerializer.ReadCore[TValue](Utf8JsonReader& reader,Type returnType,JsonSerializerOptions options)
at System.Text.Json.JsonSerializer.Deserialize[TValue](String json,JsonSerializerOptions options)
at API.Data.Seed.SeedQuestions(DataContext context) in C:\Users\fahua\Documents\Triviatandem\API\Data\Seed.cs:line 20
at API.Program.Main(String[] args) in C:\Users\fahua\Documents\Triviatandem\API\Program.cs:line 26
解决方法
Incorrect
类中的 AppQuestion
属性是IncorrectAnswer
对象的集合,但是在您的json incorrect
中是字符串数组。
您需要更改模型或json。
,最后,我找到了一个页面,其中提到了在属性中明确说明DataMember的内容。我认为播种数据应能获得更清晰的结果,但这目前仍然有效。
public class Example
{
[DataMember(Name="Question")]
public string Question { get; set; }
[DataMember(Name="Incorrect")]
public IList<string> Incorrect { get; set; }
[DataMember(Name="Correct")]
public string Correct { get; set; }
}
public class Seed
{
public Seed()
{
}
public static async Task SeedQuestions(DataContext context)
{
if (await context.Questions.AnyAsync()) return;
var questionData = await System.IO.File.ReadAllTextAsync("Data/QuestionSeedData.json");
var myDeserializedClass = JsonSerializer.Deserialize<List<Example>>(questionData);
foreach (var item in myDeserializedClass)
{
var appQuestion = new AppQuestion();
var incorrectAnswerList = new List<IncorrectAnswer>();
appQuestion.Question = item.Question;
appQuestion.Correct = item.Correct;
foreach (var thing in item.Incorrect)
{
var incorrectAnswer = new IncorrectAnswer();
incorrectAnswer.Incorrect = thing;
incorrectAnswerList.Add(incorrectAnswer);
}
appQuestion.Incorrect = incorrectAnswerList;
context.Questions.Add(appQuestion);
}
await context.SaveChangesAsync();
}
}