C#分布式事务隔离级别问题？如何解释不同的隔离级别，结合案例。

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using System.Data.SqlClient;
using System.Transactions;

namespace MyFriend
{
/*
* --隔离级别
级别一 read uncommitted System.Transactions.IsolationLevel.ReadUncommitted --未提交读

级别二 read committed System.Transactions.IsolationLevel.ReadCommitted --提交读

级别三 repeatable read System.Transactions.IsolationLevel.RepeatableRead --可重复读

级别四 serializable System.Transactions.IsolationLevel.Serializable --可串行读
*/
public partial class frmIsolationLevel : Form
{
public frmIsolationLevel()
{
InitializeComponent();
}
private static string GetConnectionString(int i)
{
if (i == 1)
return "Data Source=.;Initial Catalog=MyFriend;User ID=sa;Password=123456";
else
return "Data Source=.;Initial Catalog=student;User ID=sa;Password=123456";
}

private void button1_Click(object sender, EventArgs e)
{
string str1 = "insert into depart values('市场部3',19,'1982-02-03')";
string str2 = "insert into info values('拉灯3','078889897878','13989889899','阿富汗捣蛋部队','999','技术部')";

SqlConnection cn1 = new SqlConnection(GetConnectionString(1)); //连接库1
cn1.Open();
TransactionOptions op = new TransactionOptions();
//op.IsolationLevel = System.Transactions.IsolationLevel.ReadCommitted; //提交读
op.IsolationLevel = System.Transactions.IsolationLevel.RepeatableRead; //提交读

using (TransactionScope ts = new TransactionScope(TransactionScopeOption.Required, op)) //创建事务代码块
{
SqlCommand cmd1 = new SqlCommand(str1, cn1);
int rowsUpdated1 = cmd1.ExecuteNonQuery();
if (rowsUpdated1 > 0)
{
SqlConnection cn2 = new SqlConnection(GetConnectionString(1));//连接库2.
cn2.Open();
SqlCommand cmd2 = new SqlCommand(str2, cn2);

int rowsUpdated2 = cmd2.ExecuteNonQuery();
if (rowsUpdated2 > 0)
{
ts.Complete();
MessageBox.Show("事务提交完成！");
}
cn2.Close();
}
}
cn1.Close();
}

}
}
//*************db如下: