ASP.NET Core EFCore 属性配置与DbContext的用法详解

public class Product{    
[Key] // 主键    
public int Id { get; set; }
[Required, MaxLength(100)] // 非空且最大长度100    
public string Name { get; set; }
[ForeignKey("CategoryId")] // 外键    
public int CategoryId { get; set; }    
public Category Category { get; set; }}

protected override void OnModelCreating(ModelBuilder modelBuilder){   
 modelBuilder.Entity<Product>(entity =>    {       
 entity.HasKey(p => p.Id); // 主键   
     entity.Property(p => p.Name)           
   .IsRequired()          
    .HasMaxLength(100);
        entity.HasOne(p => p.Category) // 一对一/多关系        
      .WithMany(c => c.Products)          
    .HasForeignKey(p => p.CategoryId); 
   });}

public class AppDbContext : DbContext{    
public DbSet<Product> Products { get; set; }    
public DbSet<Category> Categories { get; set; }
    protected override void OnConfiguring(DbContextOptionsBuilder options)        
=> options.UseSqlServer("Your_Connection_String");
    protected override void OnModelCreating(ModelBuilder modelBuilder)   
　　{        
　　// Fluent API 配置    
　　}
}

// Startup.cs
services.AddDbContext<AppDbContext>(options =>    
options.UseSqlServer(Configuration.GetConnectionString("Default")));

var products = await _context.Products.Where(p => p.Price > 50).ToListAsync();

_context.Products.Add(newProduct);
await _context.SaveChangesAsync();

services.AddDbContextPool<AppDbContext>(...);

modelBuilder.Entity<Post>()    
.HasMany(p => p.Tags)    
.WithMany(t => t.Posts)    
.UsingEntity(j => j.ToTable("PostTags"));

modelBuilder.Entity<Blog>()    
.HasDiscriminator<string>("BlogType")    
.HasValue<Blog>("Standard")    
.HasValue<RssBlog>("RSS");

modelBuilder.Entity<Post>().HasQueryFilter(p => !p.IsDeleted);