private static void MappingCategory(EntityTypeBuilder<Category> builder)
        {
            builder.ForSqlServer().Table("Category");

            builder.Key(t => t.ID);
            builder.Property(t => t.ID).ForSqlServer().UseIdentity();

            builder.Property(t => t.Name).Required().MaxLength(50);
        }
        private static void MappingArticle(EntityTypeBuilder<Article> builder)
        {
            builder.ForSqlServer().Table("Article");

            builder.Key(t => t.ID);
            builder.Property(t => t.ID).ForSqlServer().UseIdentity();
            builder.Property(t => t.Title).MaxLength(100).Required();
            builder.Property(t => t.From).MaxLength(50);
            builder.Reference(t => t.User);
        }
        private static void MappingUser(EntityTypeBuilder<User> builder)
        {
            builder.ForSqlServer().Table("User");

            builder.Key(t => t.ID);
            builder.Property(t => t.ID).ForSqlServer().UseIdentity();

            builder.Property(t => t.UserName).Required().MaxLength(20);
            builder.Property(t => t.Password).Required().MaxLength(32);
            builder.Property(t => t.Nickname).Required().MaxLength(20);
            builder.Property(t => t.Email).Required().MaxLength(100);
            builder.Property(t => t.CreateDate).Required();
            builder.Property(t => t.Avatar).MaxLength(100);
            builder.Property(t => t.Token).MaxLength(32);
        }