what is the best way to add our own namespace while generating the model via Scaffolding

[archanasoni]

Hi,

We've requierment to add using statement :
using IBM.EntityFrameworkCore

Above statement has to be added while generating the Context class via scaffolding. Till .NET 6 we implemented CSharpDbContextGenerator and added in our service, but from .NET7 we see it is part of .tt file which we are not much familior..
how can we achieve the same result now ?

public override string WriteCode(
                    IModel model,
                    string contextName,
                    string connectionString,
                    string? contextNamespace,
                    string? modelNamespace,
                    bool useDataAnnotations,
                    bool useNullableReferenceTypes,                   
                    bool suppressConnectionStringWarning,
         bool suppressOnConfiguring)
        {
            Check.NotNull(model, nameof(model));
#pragma warning disable EF1001 // Internal EF Core API usage.
            _sb = new IndentedStringBuilder();
            _sb.AppendLine("using IBM.EntityFrameworkCore;");
            //_sb.AppendLine("using IBM.EntityFrameworkCore.Storage.Internal;");
            return _sb.AppendLines(base.WriteCode(model, contextName, connectionString, contextNamespace, modelNamespace, useDataAnnotations, useNullableReferenceTypes, suppressConnectionStringWarning, suppressOnConfiguring)).ToString();
#pragma warning restore EF1001 // Internal EF Core API usage.
        }

[ajcvickers]

@archanasoni Typically, the appropriate namespaces are added based on the types in the generated code. What is the case where this is not happening?

[archanasoni]

@ajcvickers, UseDb2 and IBMDBServerType.LUW require namespace IBM.EntityFrameworkCore

 protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {
            base.OnConfiguring(optionsBuilder);
            optionsBuilder.UseDb2("Connection string", 
                p => p.SetServerInfo(IBMDBServerType.LUW));
        }

another example is:

protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            base.OnModelCreating(modelBuilder);
            modelBuilder.Entity<NET7TAB1>(entity =>
            {
                entity.HasKey(e => e.ID)
                        .ForDb2IsClustered(false);
            });
        }

[roji]

@archanasoni the UseDB2 method should be on an extension class in the Microsoft.EntityFrameworkCore, much like how UseSQLServer is. This way the method "lights up" for users automatically, without them having to explicit use an IBM-specific namespace.

[archanasoni]

Thanks @roji from the beginning we have this method and others in IBM specific namespace. For some reasons we do not wish to change.. Could you help how we can add IBM Specific namespace during the model generation ?

[roji]

Since scaffolding switched to using templates in EF 7.0, there's no longer an easy way for a provider to add arbitrary namespaces; users can easily modify the templates in any way they want (that was the point of this feature), but providers cannot.

Note that CSharpDbContextGenerator was internal in 6.0 and below; you should really try to avoid accessing/overriding internal EF APIs so that this kind of breakage doesn't happen. If you finding yourself needing to do something with an internal API, you should signal this to us so we can provide guidance on an alternative implementation, or possibly change things within EF in order to accommodate your needs.

Concretely, we may want to add a a template parameter allowing extra namespaces to be passed; CSharpModelGenerator is still internal, so that still wouldn't be sufficient as a 1st-class way for a provider to inject additional namespaces. /cc @bricelam @ajcvickers

In the meantime, if you don't want to change the namespace of your extension methods, I think you'll have to instruct your users to edit their templates to add the namespace, as per the docs.

[archanasoni]

Thanks @roji but this is a breaking change for us. We implemented internal class by going through some blog from MS but unfortunately, we are unable to find that blog now.
We may instruct our user to customize T4 for a time being.. but I'm wondering for a solution where we (provider) can add our own namespaces... and when the solution will be available.. ?
Is it possible to inherit this template and then do something to add our own namespace... ?

[roji]

@archanasoni we'll discuss this internally and post back here.

FWIW note that there's an analyzer that generates warnings whenever you use an internal EF API (e.g. anything in Internal namespaces), precisely to avoid people accidentally using it. I hope you're seeing those warnings and taking them into account.

[bricelam]

If you return a MethodCallCodeFragment with a MethodInfo from ProviderCodeGenerator.GenerateUseProvider(), we should generate the using for it... (if not, that's an EF bug.) Are you using the string overload instead?

[archanasoni]

Thanks @bricelam , we had string version that we've changed to MethodInfo now but still we don't see namespace is being generated..

//here MethoInfo is exactly same what we have for SQL Server
 private static readonly MethodInfo UseDb2MethodInfo
        = typeof(Db2DbContextOptionsExtensions).GetRuntimeMethod(
            nameof(Db2DbContextOptionsExtensions.UseDb2),
            new[] { typeof(DbContextOptionsBuilder), typeof(string), typeof(Action<Db2DbContextOptionsBuilder>) })!;


public override MethodCallCodeFragment GenerateUseProvider(
            string connectionString,
            MethodCallCodeFragment? providerOptions)
            => new (UseDb2MethodInfo,
                providerOptions == null
                    ? new object[] { connectionString }
                    : new object[] { connectionString, new NestedClosureCodeFragment("x", providerOptions) });