ASP.NET Core with MySQL

ApplicationDbContext.cs

using Microsoft.AspNetCore.Identity;
using Microsoft.AspNetCore.Identity.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore;

public class ApplicationDbContext : IdentityDbContext
{

    // ...

    protected override void OnModelCreating(ModelBuilder builder)
    {
        base.OnModelCreating(builder);

        builder.Entity<IdentityRole>(entity => entity.Property(m => m.Id).HasMaxLength(450));
        builder.Entity<IdentityRole>(entity => entity.Property(m => m.ConcurrencyStamp).HasColumnType("varchar(256)"));

        builder.Entity<IdentityUserLogin<string>>(entity =>
        {
            entity.Property(m => m.LoginProvider).HasMaxLength(127);
            entity.Property(m => m.ProviderKey).HasMaxLength(127);
        });

        builder.Entity<IdentityUserRole<string>>(entity =>
        {
            entity.Property(m => m.UserId).HasMaxLength(127);
            entity.Property(m => m.RoleId).HasMaxLength(127);
        });

        builder.Entity<IdentityUserToken<string>>(entity =>
        {
            entity.Property(m => m.UserId).HasMaxLength(127);
            entity.Property(m => m.LoginProvider).HasMaxLength(127);
            entity.Property(m => m.Name).HasMaxLength(127);
        });
    }

appsettings.json

"ConnectionStrings": {
  "DefaultConnection":"server=localhost;userid=myusername;password=mypassword;database=mydatabase;"
},

Startup.cs

// This method gets called by the runtime. Use this method to add services to the container.
public void ConfigureServices(IServiceCollection services)
{
    // Add framework services.
    services.AddDbContext<ApplicationDbContext>(options =>
        options.UseMySQL(Configuration.GetConnectionString("DefaultConnection")));