Question

我有一个存储过程，其参数没有默认值，但可以为null。但我无法弄清楚如何使用Dapper传递null。我可以在ADO中做得很好。

connection.Execute("spLMS_UpdateLMSLCarrier", new { **RouteId = DBNull.Value**, CarrierId = carrierID, UserId = userID, TotalRouteRateCarrierId = totalRouteRateCarrierId },
                                        commandType: CommandType.StoredProcedure);

例外：

System.NotSupportedException was caught
  Message=The member RouteId of type System.DBNull cannot be used as a parameter value
  Source=Dapper
  StackTrace:
       at Dapper.SqlMapper.LookupDbType(Type type, String name) in C:\Dev\dapper-git\Dapper\SqlMapper.cs:line 348
       at Dapper.SqlMapper.CreateParamInfoGenerator(Identity identity) in C:\Dev\dapper-git\Dapper\SqlMapper.cs:line 1251
       at Dapper.SqlMapper.GetCacheInfo(Identity identity) in C:\Dev\dapper-git\Dapper\SqlMapper.cs:line 908
       at Dapper.SqlMapper.Execute(IDbConnection cnn, String sql, Object param, IDbTransaction transaction, Nullable`1 commandTimeout, Nullable`1 commandType) in C:\Dev\dapper-git\Dapper\SqlMapper.cs:line 532
       at Rating.Domain.Services.OrderRatingQueueService.UpdateLMSLCarrier(Int32 totalRouteRateCarrierId, Int32 carrierID, Int32 userID) in C:\DevProjects\Component\Main\Source\Rating\Source\Rating.Domain\Services\OrderRatingQueueService.cs:line 52
       at Benchmarking.Program.OrderRatingQueue() in C:\DevProjects\Component\Main\Source\Benchmarking\Source\Benchmarking\Program.cs:line 81
       at Benchmarking.Program.Main(String[] args) in C:\DevProjects\Component\Main\Source\Benchmarking\Source\Benchmarking\Program.cs:line 28
  InnerException:

不能离开RouteId，给我一个错误，表明它是必需的。不能使用常规null或者给我另一个错误。无法更改存储过程，它不属于我。

Answer 1

我认为你应该可以通过将null转换为适当的类型来实现。我们假设RouteId是一个整数：

connection.Execute("spLMS_UpdateLMSLCarrier", new { RouteId = (int?)null, CarrierId = carrierID, UserId = userID, TotalRouteRateCarrierId = totalRouteRateCarrierId }, commandType: CommandType.StoredProcedure);

使用常规null时遇到的问题很可能是在没有强制转换的情况下使用RouteId时，编译器无法推断出匿名类型中null的类型。

如何使用Dapper传递null参数

1 个答案: