using System.ComponentModel.DataAnnotations.Schema;

[Table("Role")]
public class Role
{
   // ...
}

using Microsoft.EntityFrameworkCore;

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
    modelBuilder.Entity<Role>().ToTable("Role");
}

using System;
using System.Collections.Generic;
using System.Text;

using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;

namespace Libing.App.Models.Entities
{
    [Table("Role")]
    public class Role
    {
        [Column("RoleID")]
        public int RoleID { get; set; }

        [Required]
        [Column("RoleName",TypeName = "varchar(200)")]
        public string RoleName { get; set; }
    }
}

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
    modelBuilder.Entity<Role>().ToTable("Role");
    modelBuilder.Entity<Role>()
        .Property(t => t.RoleID)
        .HasColumnName("RoleID");
    modelBuilder.Entity<Role>()
        .Property(t => t.RoleName)
        .HasColumnName("RoleName")
        .HasColumnType("varchar(200)")
        //.HasMaxLength(200)
        .IsRequired();
}