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我是Cassandra的新手,并使用linq为我的Cassandra数据库创建了一个通用存储库。对于我的Single()方法,我传递了where条件作为参数。Cassandra:参数类型不匹配
这是我的一个方法:
Single(Expression<Func<T, bool>> exp)
这是我使用查询卡珊德拉数据库
public async Task<T> Single(Expression<Func<T, bool>> exp)
{
return await GetTable.Where<T>(exp).FirstOrDefault().ExecuteAsync();
}
这是调用一个方法,该方法的LINQ代码
public override Task OnConnected()
{
if (Context.User != null)
{
string userName = Context.User.Identity.Name;
this.Groups.Add(userName, Context.ConnectionId);
***** this is the line with the issue ******
Notification notification = Task.Run(() => _notificationRepository.Single(x => x.UserName.Equals(userName))).Result;
if (notification == null)
{
_notificationRepository.CreateInstance(new NotificationUserMapping { Connections = new string[] { Context.ConnectionId }, UserName = Context.User.Identity.Name });
}
else if (!notification.Connections.Contains(Context.ConnectionId))
{
notification.Connections.Add(Context.ConnectionId);
_notificationRepository.Save(notification);
}
}
return base.OnConnected();
}
我不断收到“参数类型不匹配”的“System.AggregateException”,我很困惑这可能来自哪里。
的数据库表列:
id uuid PRIMARY KEY,
connections list<text>,
username text
和C#POCO:
[Table(ExplicitColumns = true)]
public class ConnectionMapping
{
[Column("id")]
public Guid Id { get; set; }
[Column("connections")]
public IList<string> Connections { get; set; }
[Column("username")]
public string UserName { get; set; }
}
和异常:
at System.Linq.Expressions.Expression.Condition(Expression test, Expression ifTrue, Expression ifFalse)
at Cassandra.Mapping.MapperFactory.GetExpressionToGetColumnValueFromRow(ParameterExpression row, CqlColumn dbColumn, Type pocoDestType)
at Cassandra.Mapping.MapperFactory.CreateMapperForPoco[T](RowSet rows, PocoData pocoData)
at Cassandra.Mapping.MapperFactory.CreateMapper[T](RowSet rows)
at Cassandra.Mapping.MapperFactory.<>c__DisplayClass1`1.<GetMapper>b__0(Tuple`2 _)
at System.Collections.Concurrent.ConcurrentDictionary`2.GetOrAdd(TKey key, Func`2 valueFactory)
at Cassandra.Mapping.MapperFactory.GetMapper[T](String cql, RowSet rows)
at Cassandra.Mapping.Mapper.<>c__DisplayClass7`1.<FetchAsync>b__6(Statement s, RowSet rs)
at Cassandra.Mapping.Mapper.<>c__DisplayClass2`1.<>c__DisplayClass4.<ExecuteAsyncAndAdapt>b__1(Task`1 t2)
at Cassandra.Tasks.TaskHelper.DoNext[TIn,TOut](Task`1 task, Func`2 next)
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()
at CompanyNamespace.CompanyDomain.NotificationRepository.<SingleByUserName>d__0.MoveNext()
我在想什么。我对这些文件表示怀疑。 Cassandra和C#之间的映射规则似乎是正确的。
你能展示整个方法吗?很难说什么时候你只提供小片段。 – DavidG
您是否还可以为您收到的'AggregateException'内的异常添加堆栈跟踪?可能将我们指向正确的方向。 –