如何使用Dapper传递空参数 [英] How to pass a null parameter with Dapper

问题描述

我有一个存储过程，该存储过程的参数没有默认值，但可以为null。但我不知道如何通过Dapper传递null。我可以在ADO中做到这一点。

I have a stored procedure that has a parameter with no default value, but it can be null. But I can't figure out how to pass null with Dapper. I can do it just fine in ADO.

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: 

不能关闭RouteId，给我一个错误，指出它是必需的。无法使用常规null会给我另一个错误。无法更改存储过程，它不属于我。

Can't leave the RouteId off, gives me an error that says it's required. Can't use regular null either gives me another error. Can't change the stored procedure, it does not belong to me.

推荐答案

我认为您应该可以将 null 强制转换为适当的类型。假设RouteId为整数：

I think you should be able to do it by casting null to the appropiate type. Let's assume RouteId is an integer:

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编译器无法推断<$的类型仅在不进行强制转换的情况下使用 null 时，匿名类型的c $ c> RouteId 。

The problem you are encountering when using regular null is likely that the compiler cannot infer the type of RouteId in the anonymous type when just using null without the cast.

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