In EF Core, how to check whether a migration is needed or not?

Question

I am using Entity Framework Core in an Xamarin.iOS application.

In my core project that contains code (.netstandard 2.0) that is shared between the iOS application and other applications, I would like to know if a migration is needed so that I can perform some other operations as well.

Here is the context:

public void Initialize()
{
   using (var dbContext = new MyDbContext(m_dbContextOptions))
   {
       --> bool isNeeded = demoTapeDbContext.Database.IsMigrationNeeded()

       demoTapeDbContext.Database.Migrate();
   }
}

The closest I have found is calling the method GetPendingMigrationsAsync() and check the amount of pending migrations but I am unsure whether it is the safest way to do such check in Entity Framework:

public async Task InitializeAsync()
{
   using (var dbContext = new MyDbContext(m_dbContextOptions))
   {
       bool isMigrationNeeded = (await demoTapeDbContext.Database.GetPendingMigrationsAsync()).Any();

       demoTapeDbContext.Database.Migrate();
   }
}

Timbering

Answer 1

You are correct that the GetPendingMigrationsAsync method is what you should use. From the docs:

Asynchronously gets all migrations that are defined in the assembly but haven't been applied to the target database.

If you look at the code, you can trace how it works. It gets all of the migrations defined in your assembly and removes the ones it finds by querying the database.

Newby

Answer 2

I use the following code in DbInitializer:

public static class DbInitializer
{
    public static void Initialize(ApplicationDbContext context)
    {

        if(context.Database.GetPendingMigrations().Any()){
            context.Database.Migrate();
        }
        ...

Sheaff

In the code we had only context.Database.Migrate(); which was working fine with 1 instance of our application, but now we need have 2 instances and we are facing the error where application can not insert duplicate migration. Probably we are facing this error because both instances after deployment are trying to execute the same migration. Would this check context.Database.GetPendingMigrations().Any()) be a fix for that error as well? Would this be a fix for the issue I'm facing, the thing is we horizontally scaled our application – Papillary

Answer 3

If you are using this line for single instance of sqlserver

then Dont use --> MultipleActiveResultSets in the Connection String in LaunchSetting.json

there by its wont raise exceptipn of : Microsoft.Data.SqlClient.SqlException:

Cyan

As it’s currently written, your answer is unclear. Please edit to add additional details that will help others understand how this addresses the question asked. You can find more information on how to write good answers in the help center. – Germann