DoNotConfigureDbContextTwice.cs

internal class MyContext : DbContext
{
    // ...
    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    {
        if (!optionsBuilder.IsConfigured) // This prevents multiple configurations
        {
            optionsBuilder.UseSqlite(@"Data Source=c:\temp\mydatabase.sqlite;");
        }
        // ...
    }
}