微软企业库之数据访问模块基本使用

微软企业库的数据访问模块封装了操作数据库的若干方法，本文基于微软企业库5.0。

1、添加程序集引用

需要在项目中添加对Microsoft.Practices.EnterpriseLibrary.Common.dll以及Microsoft.Practices.EnterpriseLibrary.Data.dll程序集的引用

2、使用命名空间

using Microsoft.Practices.EnterpriseLibrary.Data;
using Microsoft.Practices.EnterpriseLibrary.Data.Sql;
using System.Data.Common;

3、配置连接字符串

<connectionStrings>
<add name="ConnectionString" connectionString="Data Source=.\sqlexpress;Initial Catalog=MySchool;Integrated Security=True" providerName="System.Data.SqlClient"/>
</connectionStrings>

4、主要方法

 Database db = DatabaseFactory.CreateDatabase("ConnectionString");

4.1 执行增删改sql语句

public int Insert(Model.Subject model)
{
string sql = "insert into subject values(@subjectname,@hours,@gradeid)";
DbCommand cmd = db.GetSqlStringCommand(sql);
db.AddInParameter(cmd, "@subjectname", DbType.String, model.SubjectName);
db.AddInParameter(cmd, "@hours", DbType.Int32, model.Hours);
db.AddInParameter(cmd, "@gradeid", DbType.Int32, model.GradeId);
return db.ExecuteNonQuery(cmd);
}

4.2 返回第1行第1列的值

public int GetCount()
{
string sql = "select count(*) from subject";
DbCommand cmd = db.GetSqlStringCommand(sql);
return Convert.ToInt32(db.ExecuteScalar(cmd));
}

4.3 返回DataSet

public DataTable GetList()
{
string sql = "SELECT [SubjectId],[SubjectName],[Hours],[GradeName] from subject inner join grade on subject.GradeId=grade.GradeId";

DbCommand cmd = db.GetSqlStringCommand(sql);
DataSet ds = db.ExecuteDataSet(cmd);
return ds.Tables[0];

}

4.4 返回IDataReader

string sql = "select * from College where CollegeId=@id";
DbCommand cmd = db.GetSqlStringCommand(sql);
db.AddInParameter(cmd,"@id",DbType.Int32,id);
using (IDataReader dr = db.ExecuteReader(cmd))
{
　　if (dr.Read())
　　{
　　　　textBox1.Text = dr[0].ToString();
　　　　textBox2.Text = dr[1].ToString();
　　}
}

4.5 执行存储过程

public int Delete(int subjectId)
{
string sql = "usp_DeleteSubject";

DbCommand cmd=db.GetStoredProcCommand(sql);

db.AddInParameter(cmd, "@subjectid", System.Data.DbType.Int32, subjectId);
return db.ExecuteNonQuery(cmd);

}

4.6 使用数据库事务

private void Transaction_Click(object sender, EventArgs e)
{
DbCommand dc1 = db.GetStoredProcCommand("usp_College_Insert");

db.AddInParameter(dc1, "@CollegeID", DbType.Int32, 7);
db.AddInParameter(dc1, "@Name", DbType.String, "文旅学院");

DbCommand dc2 = db.GetStoredProcCommand("usp_College_Insert");

db.AddInParameter(dc2, "@CollegeID", DbType.Int32, 7);
db.AddInParameter(dc2, "@Name", DbType.String, "化工学院");

using (DbConnection conn = db.CreateConnection())
{
conn.Open();
DbTransaction trans = conn.BeginTransaction();

try
{
//添加一个ID为7的学院
db.ExecuteNonQuery(dc1, trans);

//添加一个ID为7的学院,主键重复,事务将回滚
db.ExecuteNonQuery(dc2, trans);

//提交事务.
trans.Commit();
}
catch
{
//回滚
trans.Rollback();
}
conn.Close();
}

//查看数据库,数据未被添加,说明事务已回滚
ExecuteDataSet_Click(null, null);
}

4.7 将返回的数据对象化

private void DataAsObject_Click(object sender, EventArgs e)
{
var results = db.ExecuteSprocAccessor<College>("usp_College_LoadAll");

MessageBox.Show(results.ElementAt(0).ToString());
}

4.8 异步执行（企业库中的异步访问数据库只支持SQL Server）

private void Async_Click(object sender, EventArgs e)
{
//创建新的数据库连接,属性必须添加:Asynchronous Processing=true
String connectionString = @"server=.\sqlexpress; database=TestDB; Integrated Security=true; Asynchronous Processing=true";
Database Sqldb = new SqlDatabase(connectionString);
DbCommand cmd = Sqldb.GetStoredProcCommand("usp_College_LoadbyID");
Sqldb.AddInParameter(cmd, "@CollegeID", DbType.Int32, 1);

try
{
IAsyncResult result = Sqldb.BeginExecuteReader(cmd, MyEndExecuteCallback, Sqldb);
}
catch (Exception ex)
{
MessageBox.Show(ex.ToString());
}
}

//当获取完毕执行该函数

private void MyEndExecuteCallback(IAsyncResult result)
{
try
{
Database Sqldb = (Database)result.AsyncState;
IDataReader reader = db.EndExecuteReader(result);

if (reader.Read())
{
College c = new College((int)reader[0], (string)reader[1]);

MessageBox.Show(c.ToString());
}
reader.Close();
}
catch(Exception ex)
{
MessageBox.Show(ex.ToString());
}
}