EF团队推出了一套比较完整的缓存和SQL执行日志的解决方案，EFProviderWrappers。他们的做法是在原来的EF Provider之上，再加一层包装，通过这层包装拦截，进行数据缓存和日志监控。数据缓存功能与NHibernate的二级缓存相比，优势在于简单轻量。
最近在做的一个项目采用了EntityFramework4.3 Code First 模式开发，希望引入这个组件完成日志跟踪和缓存功能。
在网上搜寻EFProviderWrappers 相关资料基本上都是基于ObjectContext而不是DbContext。而且这个组件也没有更新，最新版本也是2011年4月。
有什么方法才能在EF4上正常使用呢？
现将研究的方法总结一下
<connectionStrings>
<add name="TestContext"
providerName="System.Data.SqlClient"
connectionString="Server=Wyd\Instance;Initial Catalog=DatabaseName;User ID=sa;Password=123;MultipleActiveResultSets=True"/>
</connectionStrings>
<system.data>
<DbProviderFactories>
<add name="EF Caching Data Provider"
invariant="EFCachingProvider"
description="Caching Provider Wrapper" type="EFCachingProvider.EFCachingProviderFactory, EFCachingProvider, Version=1.0.0.0, Culture=neutral, PublicKeyToken=def642f226e0e59b"/>
<add name="EF Tracing Data Provider"
invariant="EFTracingProvider"
description="Tracing Provider Wrapper" type="EFTracingProvider.EFTracingProviderFactory, EFTracingProvider, Version=1.0.0.0, Culture=neutral, PublicKeyToken=def642f226e0e59b"/>
<add name="EF Generic Provider Wrapper"
invariant="EFProviderWrapper"
description="Generic Provider Wrapper" type="EFProviderWrapperToolkit.EFProviderWrapperFactory, EFProviderWrapperToolkit, Version=1.0.0.0, Culture=neutral, PublicKeyToken=def642f226e0e59b"/>
</DbProviderFactories>
</system.data>
4.在DbContext类中 建立两个构造方法(这就是关键处了）
1 public class TestContext : DbContext
2 {
3 public TestContext()
4 {
5 }
6 public TestContext(DbConnection conn)
7 :Base(conn,True)
8 {
9 }
10 }
5. OverLoad the DbConnection.
1 using (var context = new TextContext(CreateConnectionWrapper(@"name=TestContext")))
2 {
3 var product = context.ProductCollection.Find(1);
4 }
6. 添加CreateConnectionWrapper 方法
private static DbConnection CreateConnectionWrapper(string nameOrConnectionString)
{
var providerInvariantName ="System.Data.SqlClient";
var connectionString = nameOrConnectionString; //name=connectionName format
var index = nameOrConnectionString.IndexOf('=');
if (nameOrConnectionString.Substring(0,index).Trim().Equals("name", StringComparison.OrdinalIgnoreCase))
{
nameOrConnectionString=nameOrConnectionString.Substring(index + 1).Trim();
}
//look up connection string name
var connectionStringSetting = ConfigurationManager.ConnectionStrings[nameOrConnectionString];
if (connectionStringSetting != null)
{
providerInvariantName = connectionStringSetting.ProviderName;
connectionString = connectionStringSetting.ConnectionString;
}
//create the special connection string with the provider name in it
var wrappedConnectionString = wrappedProvider=" + providerInvariantName + ";" + connectionString;
//create the tracing wrapper
var connection = new EFTracingConnection
{
ConnectionString = wrappedConnectionString };
//写日志logging
connection.CommandFinished += (sender, args) => Console.WriteLine(args.ToTraceString());
return connection;
}
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