[英]Update just one field in Entity Framework 6
我已经尝试过本教程,但是对我来说不起作用( 链接 ),我的目标是仅更新实体的一个字段,而没有其他字段。 我正在测试EntityFramework,我想检查是否可以对DTO进行自动映射,并在更新一个字段后进行自动映射。
我已经试过了:
MyContext db = new MyContext();
MyClass sampleModel = new MyClass();
sampleModel.IdMyClass = "1d1ba1f2-8c08-c334-5486-08d16fecc6e3"; //GUID
sampleModel.ModificationDate = DateTime.Now;
db.MyClass.Attach(sampleModel);
db.Entry(sampleModel).Property(x => x.ModificationDate).IsModified = true;
db.SaveChanges();
MyClass类别
public partial class MyClass
{
public string IdMyClass { get; set; }
public string Name { get; set; }
public System.DateTime ModificationDate { get; set; }
public virtual ICollection<OtherClass> OtherClass{ get; set; }
}
MyClassMap
public MyClassMap() : EntityTypeConfiguration<MyClass>
{
//Primary Key
this.HasKey(t => t.IdMyClass);
//Properties
this.Property(t => t.Name)
.IsRequired()
.HasMaxLength(256);
// Table & Column Mappings
this.ToTable("MyClass");
this.Property(t => t.IdMyClass).HasColumnName("IdMyClass");
this.Property(t => t.Name).HasColumnName("Name");
this.Property(t => t.ModificationDate).HasColumnName("ModificationDate");
}
我的问题在哪里?
错误详细信息,它发生在db.SaveChanges()中
EntityFramework.dll中发生类型为'System.Data.Entity.Validation.DbEntityValidationException'的异常,但未在用户代码中处理
附加信息:对一个或多个实体的验证失败。 有关更多详细信息,请参见'EntityValidationErrors'属性。
EntityValidationErrors为空...
您可以定义将使用以下内容更新的属性:
MyContext db = new MyContext();
MyClass sampleModel = new MyClass();
sampleModel.IdMyClass = "1d1ba1f2-8c08-c334-5486-08d16fecc6e3"; //GUID
sampleModel.ModificationDate = DateTime.Now;
sampleModel.Name=string.Empty; //should not be needed
db.MyClass.Attach(sampleModel);
var entry=db.Entry(sampleModel);
entry.State = EntityState.Modified;
var excluded = new string[] { "Name" };
foreach (var name in excluded)
{
entry.Property(name).IsModified = false;
}
db.SaveChanges();
好的,这是我的代码版本。 班级
public partial class MyClass
{
public string IdMyClass { get; set; }
public string Name { get; set; }
public System.DateTime ModificationDate { get; set; }
public ICollection<OtherClass> OtherClass { get; set; }
}
public partial class OtherClass
{
public int Id { get; set; }
public string Stuff { get; set; }
}
public class MyContext : DbContext
{
public MyContext()
: base("MyContextDb")
{
}
public DbSet<MyClass> MyClasses { get; set; }
public DbSet<OtherClass> OtherClasses { get; set; }
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Entity<MyClass>().ToTable("MyClass");
modelBuilder.Entity<MyClass>()
.HasKey(t => t.IdMyClass)
.Property(t => t.Name)
.IsRequired()
.HasMaxLength(256);
modelBuilder.Entity<MyClass>().Property(t => t.IdMyClass).HasColumnName("IdMyClass");
modelBuilder.Entity<MyClass>().Property(t => t.Name).HasColumnName("Name");
modelBuilder.Entity<MyClass>().Property(t => t.ModificationDate).HasColumnName("ModificationDate");
}
}
一个简单的控制台程序来测试结果
class Program
{
static void Main(string[] args)
{
MyContext db = null; ;
try
{
db = new MyContext();
Foo(db);
Console.WriteLine("Id\tDate\tName");
foreach(var c in db.MyClasses)
{
Console.WriteLine("{0}\t{1}\t{2}",c.IdMyClass,c.ModificationDate,c.Name);
}
}
catch (Exception ex)
{
Console.WriteLine(ex.Message);
}
finally
{
if (db != null)
{
db.Dispose();
}
}
Console.ReadLine();
}
static void Foo(MyContext db)
{
var sampleModel = new MyClass();
sampleModel.IdMyClass = "1d1ba1f2-8c08-c334-5486-08d16fecc6e3"; //GUID
sampleModel.ModificationDate = DateTime.Now;
sampleModel.Name = string.Empty; //should not be needed
db.MyClasses.Attach(sampleModel);
var entry = db.Entry(sampleModel);
entry.State = EntityState.Modified;
var excluded = new string[] { "Name" };
foreach (var name in excluded)
{
entry.Property(name).IsModified = false;
}
db.SaveChanges();
}
}
希望能有所帮助。
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.