ORM框架学习之EF
2024-08-22 20:25:03
首先推荐一篇很好的EF文章翻译，可以系统的学习一遍。
《Entity Framework 6 Recipes》中文翻译系列
EF使用体会
优点：
- 可以省去Ado.net复杂的管道连接代码。
- 通过简单的引用就能完成对数据库的连接和开发。
- 可以省去一些SQL语句的编写，对一些底层可能需要适配多数据库提供了一些方便。
缺点：
- 学习成本较高，如果不怎么懂SQL，索引的一些数据库知识，也写不太好相对优化的Linq查询，所有EF既要懂Sql又懂Linq是最好的。
- 比较大，EF的dll默认是连接SqlServer若要连接其它数据库引用其它数据库的DLL加起来10几M，而像Dapper这样的轻量级框架才100多K。
- 查询只支持数据结果对实体的转换，不支持DataTable。
资料汇总
EF连接
EF配置
EF进阶
1.学习LINQ To Sql
2.学习Expression
3.优化测试
简单的类库
项目如图：
Data.Map中放相关的EntityTypeConfiguration
Data.Module中相关的实体
这里贴一下EFContext和EFDatabase的类
using System;
using System.Collections.Generic;
using System.Data.Entity;
using System.Data.Entity.ModelConfiguration;
using System.Linq;
using System.Reflection;
using System.Text;
using System.Threading.Tasks;
namespace Data.EF
{
//[DbConfigurationType(typeof(MySql.Data.Entity.MySqlEFConfiguration))] Mysql数据库配置
public class EFContext : DbContext, IDisposable
{
public EFContext(string dbName)
: base(dbName)
{
Database.SetInitializer<EFContext>(null);
this.Configuration.AutoDetectChangesEnabled = false;
this.Configuration.ValidateOnSaveEnabled = false;
this.Configuration.LazyLoadingEnabled = false;
this.Configuration.ProxyCreationEnabled = false;
}
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
string assembleFileName = Assembly.GetExecutingAssembly().CodeBase.Replace("Data.EF.DLL", "Data.Map.dll").Replace("file:///", "");
Assembly asm = Assembly.LoadFile(assembleFileName);
var typesToRegister = asm.GetTypes()
.Where(type => !String.IsNullOrEmpty(type.Namespace))
.Where(type => type.BaseType != null && type.BaseType.IsGenericType && type.BaseType.GetGenericTypeDefinition() == typeof(EntityTypeConfiguration<>));
foreach (var type in typesToRegister)
{
dynamic configurationInstance = Activator.CreateInstance(type);
modelBuilder.Configurations.Add(configurationInstance);
}
base.OnModelCreating(modelBuilder);
}
}
}
using System;
using System.Collections;
using System.Collections.Generic;
using System.Data;
using System.Data.Common;
using System.Data.Entity;
using System.Data.Entity.Core.Metadata.Edm;
using System.Data.Entity.Infrastructure;
using System.Linq;
using System.Linq.Expressions;
using System.Reflection;
using System.Text;
namespace Data.EF
{
public class EFDatabase
{
/// <summary>
/// 返回字符集
/// </summary>
/// <typeparam name="Table"></typeparam>
/// <returns></returns>
public DbSet<Table> Set<Table>() where Table : class
{
return dbcontext.Set<Table>();
}
#region 属性
/// <summary>
/// 获取 当前使用的数据访问上下文对象
/// </summary>
public DbContext dbcontext { get; set; }
/// <summary>
/// 事务对象
/// </summary>
public DbTransaction dbTransaction { get; set; }
#endregion
#region 构造函数
public EFDatabase(string dataBase)
{
dbcontext = new EFContext(dataBase);
}
#endregion
#region 私有方法
/// <summary>
/// 获取实体类键值（缓存）
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="entity"></param>
/// <returns></returns>
private static Hashtable GetPropertyInfo<T>(T entity)
{
Type type = entity.GetType();
object CacheEntity = null;
if (CacheEntity == null)
{
Hashtable ht = new Hashtable();
PropertyInfo[] props = type.GetProperties();
foreach (PropertyInfo prop in props)
{
string name = prop.Name;
object value = prop.GetValue(entity, null);
ht[name] = value;
}
return ht;
}
else
{
return (Hashtable)CacheEntity;
}
}
/// <summary>
/// 存储过程语句
/// </summary>
/// <param name="procName">存储过程名称</param>
/// <param name="dbParameter">执行命令所需的sql语句对应参数</param>
/// <returns></returns>
private static string BuilderProc(string procName, params DbParameter[] dbParameter)
{
StringBuilder strSql = new StringBuilder("exec " + procName);
if (dbParameter != null)
{
foreach (var item in dbParameter)
{
strSql.Append(" " + item + ",");
}
strSql = strSql.Remove(strSql.Length - 1, 1);
}
return strSql.ToString();
}
private int Delete<T>(T entity) where T : class
{
dbcontext.Set<T>().Attach(entity);
dbcontext.Set<T>().Remove(entity);
return dbTransaction == null ? dbcontext.SaveChanges() : 0;
}
private int Delete<T>(IEnumerable<T> entities) where T : class
{
foreach (var entity in entities)
{
dbcontext.Set<T>().Attach(entity);
dbcontext.Set<T>().Remove(entity);
}
return dbTransaction == null ? dbcontext.SaveChanges() : 0;
}
#endregion
public EFDatabase BeginTrans()
{
DbConnection dbConnection = ((IObjectContextAdapter)dbcontext).ObjectContext.Connection;
if (dbConnection.State == ConnectionState.Closed)
{
dbConnection.Open();
}
dbTransaction = dbConnection.BeginTransaction();
return this;
}
public int Commit()
{
try
{
int returnValue = dbcontext.SaveChanges();
if (dbTransaction != null)
{
dbTransaction.Commit();
this.Close();
}
return returnValue;
}
catch (Exception ex)
{
if (ex.InnerException != null )
{
throw ex.InnerException;
}
throw;
}
finally
{
if (dbTransaction == null)
{
this.Close();
}
}
}
public void Rollback()
{
this.dbTransaction.Rollback();
this.dbTransaction.Dispose();
this.Close();
}
public void Close()
{
dbcontext.Dispose();
}
public int ExecuteBySql(string strSql)
{
dbcontext.Database.CommandTimeout = 60;
return dbcontext.Database.ExecuteSqlCommand(strSql);
}
public int ExecuteBySql(string strSql, params object[] dbParameter)
{
dbcontext.Database.CommandTimeout = 60;
return dbcontext.Database.ExecuteSqlCommand(strSql, dbParameter);
}
public int ExecuteByProc(string procName)
{
return dbcontext.Database.ExecuteSqlCommand(BuilderProc(procName));
}
public int ExecuteByProc(string procName, System.Data.Common.DbParameter[] dbParameter)
{
return dbcontext.Database.ExecuteSqlCommand(BuilderProc(procName, dbParameter), dbParameter);
}
public T FindEntity<T>(object keyValue) where T : class
{
return dbcontext.Set<T>().Find(keyValue);
}
public T FindEntity<T>(Expression<Func<T, bool>> condition) where T : class, new()
{
return dbcontext.Set<T>().Where(condition).FirstOrDefault();
}
public IQueryable<T> FindList<T>(Expression<Func<T, bool>> condition) where T : class, new()
{
return dbcontext.Set<T>().Where(condition);
}
public IQueryable<T> FindList<T>(string strSql) where T : class
{
return dbcontext.Set<T>().SqlQuery(strSql).AsQueryable();
}
public IQueryable<T> FindList<T>(string strSql, DbParameter[] dbParameter) where T : class
{
return dbcontext.Set<T>().SqlQuery(strSql, dbParameter).AsQueryable();
}
public int Delete<T>(object propertyValue, string propertyName) where T : class
{
string TableName = typeof(T).Name;
return this.ExecuteBySql("delete from " + TableName + " where " + propertyName + " = {0}", propertyValue);
}
public int Delete<T>(Expression<Func<T, bool>> condition) where T : class, new()
{
IEnumerable<T> entities = dbcontext.Set<T>().Where(condition).ToList();
return entities.Count() > 0 ? Delete(entities) : 0;
}
public int Update<T>(T entity) where T : class
{
dbcontext.Set<T>().Attach(entity);
Hashtable props = GetPropertyInfo<T>(entity);
foreach (string item in props.Keys)
{
object value = dbcontext.Entry(entity).Property(item).CurrentValue;
if (value != null)
{
if (value.ToString() == " "||value.ToString().Trim()=="")
dbcontext.Entry(entity).Property(item).CurrentValue = null;
dbcontext.Entry(entity).Property(item).IsModified = true;
}
}
return dbTransaction == null ? this.dbcontext.SaveChanges() : 0;
}
public int Update<T>(IEnumerable<T> entities) where T : class
{
foreach (var entity in entities)
{
this.Update(entity);
}
return dbTransaction == null ? this.dbcontext.SaveChanges() : 0;
}
}
}
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