How to pass a null parameter with Dapper

Question

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); ``` Exception: ``` 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…

Accepted Answer

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);
```

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.

How to pass a null parameter with Dapper

Solution

Problem