本文介绍了实体框架 4:如何找到主键?的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
我正在尝试使用 EF4 创建一个通用方法来查找对象的主键.
I am trying to create a generic method using EF4 to find the primary key of an object.
示例
public string GetPrimaryKey<T>()
{
...
}
为了提供更多信息,我正在使用 Tekpub StarterKit,下面是我正在尝试启动和运行的类
To give more info I am working off of the Tekpub StarterKit and below is the class I am trying to get up and running
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Data.Objects;
using System.Data.Objects.ELinq;
using System.Data.Linq;
using Web.Infrastructure.Storage.EF4;
namespace Web.Infrastructure.Storage {
public class EFSession:ISession {
PuzzleEntities _db;//This is an ObjectContext
public EFSession() {
_db = new PuzzleEntities();
}
public void CommitChanges() {
_db.SaveChanges();
}
/// <summary>
/// Gets the table provided by the type T and returns for querying
/// </summary>
private ObjectSet<T> GetObjectSet<T>() where T:class {
return _db.CreateObjectSet<T>();
}
private T GetByPrimaryKey<T>() where T: class
{
.....
}
public void Delete<T>(System.Linq.Expressions.Expression<Func<T, bool>> expression) where T: class{
foreach (T item in All<T>().Where(expression))
{
GetObjectSet<T>().DeleteObject(item);
}
}
public void Delete<T>(T item) where T : class {
GetObjectSet<T>().DeleteObject(item);
}
public void DeleteAll<T>() where T : class {
foreach(T item in All<T>())
{
GetObjectSet<T>().DeleteObject(item);
}
}
public void Dispose() {
_db.Dispose();
}
public T Single<T>(System.Linq.Expressions.Expression<Func<T, bool>> expression) where T:class {
return GetObjectSet<T>().SingleOrDefault(expression);
}
public IQueryable<T> All<T>() where T : class {
return GetObjectSet<T>().AsQueryable();
}
public void Add<T>(T item) where T : class {
GetObjectSet<T>().AddObject(item);
}
public void Add<T>(IEnumerable<T> items) where T : class {
foreach (T item in items)
{
GetObjectSet<T>().AddObject(item);
}
}
public void Update<T>(T item) where T : class {
//nothing needed here
}
}
}
推荐答案
所以我终于找到了如何让它工作的方法.我希望我没有丢失昨晚阅读的博客的链接,因为我没有编写代码.
So I was finally able to find out how to get this to work. I wish I hadn't lost the link to the blog I read last night as I didn't write the code.
public T GetByPrimaryKey<T>(int id) where T : class
{
return (T)_db.GetObjectByKey(new EntityKey(_db.DefaultContainerName + "." + this.GetEntityName<T>(), GetPrimaryKeyInfo<T>().Name, id));
}
string GetEntityName<T>()
{
string name = typeof(T).Name;
if (name.ToLower() == "person")
return "People";
else if (name.Substring(name.Length - 1, 1).ToLower() == "y")
return name.Remove(name.Length - 1, 1) + "ies";
else if (name.Substring(name.Length - 1, 1).ToLower() == "s")
return name + "es";
else
return name + "s";
}
private PropertyInfo GetPrimaryKeyInfo<T>()
{
PropertyInfo[] properties = typeof(T).GetProperties();
foreach (PropertyInfo pI in properties)
{
System.Object[] attributes = pI.GetCustomAttributes(true);
foreach (object attribute in attributes)
{
if (attribute is EdmScalarPropertyAttribute)
{
if ((attribute as EdmScalarPropertyAttribute).EntityKeyProperty == true)
return pI;
}
else if (attribute is ColumnAttribute)
{
if ((attribute as ColumnAttribute).IsPrimaryKey == true)
return pI;
}
}
}
return null;
}
我希望这对其他人有帮助.我只能说它应该更清楚如何做到这一点.
I hope this helps someone else. All I can say is that it should be a little clearer on how to do this.
这篇关于实体框架 4:如何找到主键?的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持!