EF唯一索引
this.Property(p => p.Name) .IsRequired() .HasMaxLength(new int?(50)) .HasColumnAnnotation("Index", new IndexAnnotation(new IndexAttribute("UX_Role_Name") { IsUnique=true}));
using System.ComponentModel.DataAnnotations.Schema; [Index(IsUnique = true)]
[ForeignKey(nameof(SchoolId))]