Npgsql error - The store type 'nvarchar(MAX)' could not be found in the Npgsql provider manifest - npgsql

Question

I'm new to Postgres and using npgsql as the provider to EF6. Just to provide some context, I've recently migrated our SQL Server to Aurora Postgres using the AWS DMS. That seems to be all good; I can see data and tables, etc...Now, I'm trying to hook up our application (in C# using EF6) to switch over to the Postgres DB. I've gone through all the steps to setup npgsql and npgsql EF provider, and making a new additional db context to connect to the Postgres DB. All seems good at this point.
I decided to do a simple EF query to fetch.
var courses = context.Courses.FirstOrDefault();
I got this exception:
An Internal Server Error has occurred|System.InvalidOperationException: The store type 'nvarchar(MAX)' could not be found in the Npgsql provider manifest
at System.Data.Entity.Utilities.DbProviderManifestExtensions.GetStoreTypeFromName(DbProviderManifest providerManifest, String name)
at System.Data.Entity.ModelConfiguration.Configuration.Properties.Primitive.PrimitivePropertyConfiguration.ConfigureColumn(EdmProperty column, EntityType table, DbProviderManifest providerManifest)
at System.Data.Entity.ModelConfiguration.Configuration.Properties.Primitive.PrimitivePropertyConfiguration.<>c__DisplayClass47_0.<Configure>b__0(Tuple`2 pm)
at System.Data.Entity.Utilities.IEnumerableExtensions.Each[T](IEnumerable`1 ts, Action`1 action)
at System.Data.Entity.ModelConfiguration.Configuration.Types.StructuralTypeConfiguration.ConfigurePropertyMappings(IList`1 propertyMappings, DbProviderManifest providerManifest, Boolean allowOverride)
at System.Data.Entity.ModelConfiguration.Configuration.Types.EntityTypeConfiguration.ConfigurePropertyMappings(DbDatabaseMapping databaseMapping, EntityType entityType, DbProviderManifest providerManifest, Boolean allowOverride)
at System.Data.Entity.ModelConfiguration.Configuration.Types.EntityTypeConfiguration.Configure(EntityType entityType, DbDatabaseMapping databaseMapping, DbProviderManifest providerManifest)
at System.Data.Entity.ModelConfiguration.Configuration.ModelConfiguration.ConfigureEntityTypes(DbDatabaseMapping databaseMapping, ICollection`1 entitySets, DbProviderManifest providerManifest)
at System.Data.Entity.ModelConfiguration.Configuration.ModelConfiguration.Configure(DbDatabaseMapping databaseMapping, DbProviderManifest providerManifest)
at System.Data.Entity.DbModelBuilder.Build(DbProviderManifest providerManifest, DbProviderInfo providerInfo)
at System.Data.Entity.DbModelBuilder.Build(DbConnection providerConnection)
at System.Data.Entity.Internal.LazyInternalContext.CreateModel(LazyInternalContext internalContext)
at System.Data.Entity.Internal.RetryLazy`2.GetValue(TInput input)
at System.Data.Entity.Internal.LazyInternalContext.InitializeContext()
at System.Data.Entity.Internal.InternalContext.Initialize()
at System.Data.Entity.Internal.InternalContext.GetEntitySetAndBaseTypeForType(Type entityType)
at System.Data.Entity.Internal.Linq.InternalSet`1.Initialize()
at System.Data.Entity.Internal.Linq.InternalSet`1.get_InternalContext()
at System.Data.Entity.Infrastructure.DbQuery`1.System.Linq.IQueryable.get_Provider()
at System.Data.Entity.QueryableExtensions.CountAsync[TSource](IQueryable`1 source, CancellationToken cancellationToken)
at System.Data.Entity.QueryableExtensions.CountAsync[TSource](IQueryable`1 source)
Anyone know what this means?

Answer 1

Take a look at these EF docs on how to manage migrations with multiple databases.