System.DllNotFoundException: Unable to load DLL ‘sni.dll’ or one of its dependencies: The specified module could n ot be found. (0x8007007E)

This message happens when deploying my .NET Core 3.1 application to production (when compiling the code to an .exe file), but not when running the application locally.

It turns out, that Dapper is missing a reference to System.Data.SqlClient. Adding the System.Data.SqlClient NuGet package to the project solves the issue:

System.Data.SqlClient

The full error message is:

Unhandled exception. Unhandled exception. System.TypeInitializationException: The type initializer for ‘System.Data.SqlClient.TdsParser’ threw an exception.
—> System.TypeInitializationException: The type initializer for ‘System.Data.SqlClient.SNILoadHandle’ threw an exception.
—> System.DllNotFoundException: Unable to load DLL ‘sni.dll’ or one of its dependencies: The specified module could not be found. (0x8007007E)
at System.Data.SqlClient.SNINativeMethodWrapper.SNIInitialize(IntPtr pmo)
at System.Data.SqlClient.SNINativeMethodWrapper.SNIInitialize()
at System.Data.SqlClient.SNILoadHandle..ctor()
at System.Data.SqlClient.SNILoadHandle..cctor()
— End of inner exception stack trace —
at System.Data.SqlClient.TdsParser..cctor()
— End of inner exception stack trace —
at System.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection owningObject, UInt32 waitForMultipleObject
sTimeout, Boolean allowCreate, Boolean onlyOneCheckConnection, DbConnectionOptions userOptions, DbConnectionInternal& co
nnection)
at System.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection owningObject, TaskCompletionSource`1 retry
, DbConnectionOptions userOptions, DbConnectionInternal& connection)
at System.Data.ProviderBase.DbConnectionFactory.TryGetConnection(DbConnection owningConnection, TaskCompletionSource`
1 retry, DbConnectionOptions userOptions, DbConnectionInternal oldConnection, DbConnectionInternal& connection)
at System.Data.ProviderBase.DbConnectionInternal.TryOpenConnectionInternal(DbConnection outerConnection, DbConnectionFactory connectionFactory, TaskCompletionSource`1 retry, DbConnectionOptions userOptions)
at System.Data.ProviderBase.DbConnectionClosed.TryOpenConnection(DbConnection outerConnection, DbConnectionFactory connectionFactory, TaskCompletionSource`1 retry, DbConnectionOptions userOptions) at System.Data.SqlClient.SqlConnection.TryOpen(TaskCompletionSource`1 retry)
at System.Data.SqlClient.SqlConnection.Open()
at Dapper.SqlMapper.QueryImpl[T](IDbConnection cnn, CommandDefinition command, Type effectiveType)+MoveNext() in C:\projects\dapper\Dapper\SqlMapper.cs:line 1079
at System.Collections.Generic.List`1..ctor(IEnumerable`1 collection)
at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)
at Dapper.SqlMapper.Query[T](IDbConnection cnn, String sql, Object param, IDbTransaction transaction, Boolean buffered, Nullable`1 commandTimeout, Nullable`1 commandType) in C:\projects\dapper\Dapper\SqlMapper.cs:line 721

MORE TO READ:

• Dapper Github Repo
• System.Data.SqlClient Github Repo
• Unable to load DLL ‘sni.dll’ on .NET Core 2.0 from GitHub
• Unable to load DLL ‘sni.dll’ – Entity Framework Core from StackOverflow
• [SOLVED] Unable to load sni.dll in azure Webjob from Tutel.me

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