EF Core 7.0 新特性之批量修改

概要

EF Core 7.0 提供了一个可以将LINQ查询和批量修改相结合的方法ExecuteUpdate。由于数据修改是以批量更新的方式完成，所以可以减少数据库的往返次数。

本文将主要介绍ExecuteUpdate的使用方法。

代码和实现

基本案例

本文我们使用银行分行，ATM机和分行经理三张数据表，关系如下，类定义请见附录：

1. 一个分行拥有若干台ATM机
2. 一台ATM机只能隶属于一个分行
3. 一个分行只拥有一名分行经理
4. 一个人只能做一个分行的经理

批量更新之单表操作

我们在所有IsDeleted 为true，即已经关闭的分行, 将它们的名称前面加上字符串 Decommissioned

EF CORE代码如下：

public async Task<int> UpdateBranchSingleTable()
{
    return await _context.Set<Branch>()
            .Where(b => b.IsDeleted == true)
            .ExecuteUpdateAsync(b => b.SetProperty(p => p.Name, m => "Decommissioned" +  m.Name + "!"));    
}
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生成的SQL代码如下：

UPDATE [t]
	SET [t].[Name] = (N'Decommissioned' + [t].[Name]) + N'!'
	FROM [tt_branch] AS [t]
WHERE [t].[IsDeleted] = CAST(1 AS bit)
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生成的是批量更新的SQL语句。

批量更新之多表操作

Case 1 查询拥有支持外币操作ATM机的分行，并将分行名称前面标注支持外币业务。

 public async Task<int> UpdateBranchFormMultipleTable()
 {
     return await _context.Set<Branch>()
              .Where(b => b.IsDeleted == false && b.Atms.Any(a => a.SupportForeignCurrency == true))
              .ExecuteUpdateAsync(b => b.SetProperty(p => p.Name, m => "Global Service " + m.Name));    
  }
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Case 2 查询分行经理title是BranchManager的分行，并将这些分行的名称前面增加Level 2。

 public async Task<int> UpdateBranchMultipleTables() {
     return await _context.Set<Branch>()
             .Where(b => b.IsDeleted == false && b.Manager.Title == "BranchManager")
             .ExecuteUpdateAsync(b => b.SetProperty(p => p.Name, m => "Level 2" + m.Name));
 }
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生成的SQL代码如下：

UPDATE [t]
 	SET [t].[Name] = N'Level 2' + [t].[Name]
 	FROM [tt_branch] AS [t]
 	INNER JOIN [tt_user] AS [t0] ON [t].[Id] = [t0].[Id]
WHERE [t].[IsDeleted] = CAST(0 AS bit) AND [t0].[Title] = N'BranchManager'
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我们看到，SQL是基于联表操作以后再进行的过滤和更新。这样看，通过Dapple等半自动ORM框架，自己完成的SQL语句和通过EF Core生成的SQL没有任何区别。

附录

实体类定义

public class Entity
{
	 [Key]
	 [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
	 public int Id { get; set; }
	 [Timestamp]
	 public byte[]? Rowversion { get; set; }
	 public bool IsDeleted { get; set; }
}

 [Table("tt_branch")]
  public class Branch : Entity
  {
     [Required]
     public string Name { get; set; } = string.Empty;
     [Required]
     public string Address { get; set; } = string.Empty;
     [Required]
     public bool hasCreditCardService { get; set; } = false;
     [Required]
     public bool hasChequeService { get; set; } = false;
     public ICollection<ATM> Atms { get; } = new List<ATM>();
     public User Manager { get; set; } = null!;
}
public abstract class BankDevice : Entity
{
	 [Required]
	 public string Name { get; set; } = string.Empty;
	 [Required]
	 public DeviceStatus DeviceStatus { get; set; } = DeviceStatus.Running;
 }
 [Table("tt_atm")]
 public class ATM : BankDevice
 {
     [Required]
     public bool SupportForeignCurrency { get; set; } = false;
 }
public enum DeviceStatus
{
    Running = 1,
    Standby,
    Maintance
}

[Table("tt_user")]
public class User:Entity
{
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public string Title { get; set; }
    public Branch Branch { get; set; } = null!;
}
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实体关系定义

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
      modelBuilder.Entity<Branch>()
          .HasMany(x => x.Atms)
          .WithOne()
          .HasForeignKey("BranchId")
          .IsRequired();
      modelBuilder.Entity<Branch>()
          .HasMany(x => x.Cdms)
          .WithOne()
          .HasForeignKey("BranchId")
          .IsRequired();
      modelBuilder.Entity<Branch>()
         .HasMany(x => x.MCAtms)
         .WithOne()
         .HasForeignKey("BranchId")
         .IsRequired();

      modelBuilder.Entity<Branch>()
       .HasOne(x => x.Manager)
       .WithOne(x => x.Branch)
       .HasForeignKey<Branch>();
  }
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