我遇到了一个奇怪的问题,即我能够将调用的结果返回到存储过程,但代码追溯失败。SqlDataReader的连接属性为空
public IEnumerable<T> ExecuteStoredProcedure<T>(string storedProcedureName, IDataMapper<T> mapper, IDictionary<string, object> parameters)
{
using (var connection = new SqlConnection(connectionString))
{
using (var cmd = new SqlCommand(storedProcedureName, connection))
{
cmd.CommandType = CommandType.StoredProcedure;
foreach (var key in parameters.Keys)
{
cmd.Parameters.AddWithValue(key, parameters[key]);
}
connection.Open();
SqlDataReader reader = cmd.ExecuteReader();
//return MapRecordsToDTOs(reader, mapper);
//let's test:
IEnumerable<T> result = MapRecordsToDTOs(reader, mapper);
var x = (new List<T>(result)).Count;
System.Diagnostics.Debug.WriteLine(x);
return result;
}
}
}
private static IEnumerable<T> MapRecordsToDTOs<T>(SqlDataReader reader, IDataMapper<T> mapper)
{
if (reader.HasRows)
{
while (reader.Read())
{
System.Diagnostics.Debug.WriteLine(reader["Id"]); //what's going on...
yield return mapper.MapToDto((IDataRecord)reader);
}
}
}
调用此代码显示了可变x
始终表示,我期望从我的存储过程的调用看到的行数。
另外我的调试输出显示了我期望看到的ID值。
但是,在返回这些结果之后,我会从行if (reader.HasRows)
(即已执行的行)收到错误An exception of type 'System.InvalidOperationException' occurred in System.Data.dll but was not handled in user code
。我从中调用此请求的浏览器显示HTTP Error 502.3 - Bad Gateway
。
我怀疑的原因是系统的计算调试ID
和X
值分别对它将如何返回真实用户输出。因此,它执行一个懒惰的操作来获取IEnumerable值到它必须返回的位置;只有在这一点上,using
语句才导致调用处理方法,因此读者的连接为空(这是我在调试时检查reader
变量的属性时看到的内容)。
有没有人见过这样的行为/是它的错误;或者我错过了一些明显的东西?
附加代码:
public interface IDataMapper<T>
{
T MapToDto(IDataRecord record);
}
public class CurrencyMapper: IDataMapper<CurrencyDTO>
{
const string FieldNameCode = "Code";
const string FieldNameId = "Id";
const string FieldNameName = "Name";
const string FieldNameNum = "Num";
const string FieldNameE = "E";
const string FieldNameSymbol = "Symbol";
public CurrencyMapper() { }
public CurrencyDTO MapToDto(IDataRecord record)
{
var code = record[FieldNameCode] as string;
var id = record[FieldNameId] as Guid?;
var name = record[FieldNameName] as string;
var num = record[FieldNameNum] as string;
var e = record[FieldNameE] as int?;
var symbol = record[FieldNameSymbol] as char?;
return new CurrencyDTO(id, code, num, e, name, symbol);
}
}
public class CurrencyRepository
{
const string SPReadAll = "usp_CRUD_Currency_ReadAll";
readonly SqlDatabase db;
public CurrencyRepository()
{
db = new SqlDatabase(); //stick to SQL only for the moment for simplicity
}
public IEnumerable<CurrencyDTO> GetCurrencyCodes()
{
var mapper = new CurrencyMapper();
return db.ExecuteStoredProcedure(SPReadAll, mapper);
}
}
public class CurrencyDTO
{
readonly Guid? id;
readonly string code;
readonly string num;
readonly int? e;
readonly string name;
readonly char? symbol;
public CurrencyDTO(Guid? id,string code,string num,int? e,string name, char? symbol)
{
this.id = id;
this.code = code;
this.num = num;
this.e = e;
this.name = name;
this.symbol = symbol;
}
public Guid? Id { get { return id; } }
public string Code { get { return code; } }
public string Num { get { return num; } }
public int? E { get { return e; } }
public string Name { get { return name; } }
public char? Symbol { get { return symbol; } }
}
你尝试检查(或者在代码中使用)刚刚SqlDataReader的读卡器= cmd.ExecuteReader后''reader.HasRows'() ;'和之前调用'MapRecordsToDTOs'? – McNets
你可以尝试:'reader = await cmd.ExecuteReaderAsync();' – McNets
@mcNets:'MapRecordsToDTOs'函数确认'reader。HasRows'是真实的,因为它能够迭代这些行以允许'x'获得正确的值,并且''''''Debug.WriteLine'正确输出'ID'。声明。 – JohnLBevan