所谓ADO.NET是一组用于和数据源进行交互的面向对象类库,就是访问数据库SQL Access 或XML Excel等数据源而已。
访问数据首先就要建立到操作对象的连接,这就是connection对象,通常用的访问SQL Server的叫SqlConnection类,访问Access的叫OleDbConnection.
连接上了,自然就要执行Sql语句来操作表,这时就需要Command对象了,同样的也分SqlCommand(访问SQLServer),OleDbCommand(访问Access或其它).
执行Sql Command的成功后有结果返回,此时需要装结果的容器了,如果是数据表则需要,一是DataReader另一个是DataSet.
DataReader来自于Command.ExecuteReader()返回,而DataSet来自于DataAdapter.Fill(ds, "dstablename")的Fill.同是存放表的.
为何要分两种呢,因为DataSet经过Fill操作后是将表拷贝至内存了,并关闭了连接,而DataReader只是打开联接,数据需要由前至后的一条条读出.在不同的应用环境需要时各有所长,特别是dataset在大量请求负载处理时将会显现出超强的性能优势,采用SqlDataAdapter.Update操作的SqlCommandBuilder来更新删除,修改一些大批量数据,或用SQL语句实现修改多列多项有困难的需求时.
使用Sql server数据库时常会用到的在webconfig中定义connectionStrings 如下
引用这个定义则用如下语句
string connectionString =ConfigurationManager.ConnectionStrings["Northwind"].ConnectionString;
通常使用SqlDataAdapter(),读取数据用GridView显示如下:
string connStr = ConfigurationManager.ConnectionStrings["Northwind"].ConnectionString;
SqlConnection myConnection = new SqlConnection(connStr);
myConnection.Open();
SqlDataAdapter da = new SqlDataAdapter("SELECT * FROM Customers; SELECT * FROM Orders;", myConnection); //注意两个表读
DataSet ds = new DataSet();
da.Fill(ds, "Customers");
CustomersGridView.DataSource = ds.Tables[0];//ds.Tables["Customers"]
CustomersGridView.DataBind();
OrdersGridView.DataSource = ds.Tables[0];//ds.Tables["Customers"]
OrdersGridView.DataBind();
myConnection.Close();
通常使用SqlDataReader(),读取数据用GridView显示时如下:
string connStr = ConfigurationManager.ConnectionStrings["Northwind"].ConnectionString;
SqlConnection myConnection = new SqlConnection(connStr);
myConnection.Open();
SqlCommand command = new SqlCommand("Select * FROM Customers", myConnection);
SqlDataReader dr=command.ExecuteReader();
GridView1.DataSource = dr;
GridView1.DataBind();
myConnection.Close();
一个基本的Sql server 采用DataReader()操作增,删,改,读的类,C#代码如下
using System;
using System.Data;
using System.Data.SqlClient;
class SqlCommandDemo
{
SqlConnection conn;
public SqlCommandDemo() //构造
{
// 建立联接方法
conn = new SqlConnection("Data Source=(local);Initial Catalog=Northwind;Integrated Security=SSPI");
}
// 主程序
static void Main()
{
SqlCommandDemo scd = new SqlCommandDemo();
Console.WriteLine();
Console.WriteLine("Categories Before Insert");
Console.WriteLine("------------------------");
//ExecuteReader 读出显示
scd.ReadData();
// 用ExecuteNonQuery 方法新建插入一条数据
scd.InsertData();
Console.WriteLine();
Console.WriteLine("Categories After Insert");
Console.WriteLine("------------------------------");
scd.ReadData();
// use ExecuteNonQuery 更新
scd.UpdateData();
Console.WriteLine();
Console.WriteLine("Categories After Update");
Console.WriteLine("------------------------------");
scd.ReadData();
// use ExecuteNonQuery 删除方法
scd.DeleteData();
Console.WriteLine();
Console.WriteLine("Categories After Delete");
Console.WriteLine("------------------------------");
scd.ReadData();
// use ExecuteScalar 统计方法
int numberOfRecords = scd.GetNumberOfRecords();
Console.WriteLine();
Console.WriteLine("Number of Records: {0}", numberOfRecords);
}
//以下各子方法
public void ReadData() //读出
{
SqlDataReader rdr = null;
try
{
conn.Open();
// 1. 初始化一个SqlCommand对象
SqlCommand cmd = new SqlCommand("select CategoryName from Categories", conn);
// 2. 读出
rdr = cmd.ExecuteReader();
// 遍历所有数据输出
while (rdr.Read())
{
Console.WriteLine(rdr[0]);
}
}
finally
{
// 关闭
if (rdr != null)
{
rdr.Close();
}
// 且关闭联接
if (conn != null)
{
conn.Close();
}
}
}
public void InsertData() //插入
{
try
{
conn.Open();
// 准备参数
string insertString = @"insert into Categories (CategoryName, Description)values ('Miscellaneous', 'Whatever doesn''t fit elsewhere')";
// 1. 初始化SqlCommand,并连接conn
SqlCommand cmd = new SqlCommand(insertString, conn);
// 2. 执行
cmd.ExecuteNonQuery();
}
finally
{
// 关闭
if (conn != null)
{
conn.Close();
}
}
}
public void UpdateData() //更新
{
try
{
conn.Open();
// 参数
string updateString = @"update Categories set CategoryName = 'Other' where CategoryName = 'Miscellaneous'";
// 1.初始化
SqlCommand cmd = new SqlCommand(updateString);
// 2. 连接conn
cmd.Connection = conn;
// 3.执行
cmd.ExecuteNonQuery();
}
finally
{
// 关闭
if (conn != null)
{
conn.Close();
}
}
}
public void DeleteData() //删除
{
try
{
conn.Open();
//准备参数
string deleteString = @"delete from Categories where CategoryName = 'Other'";
// 1. command
SqlCommand cmd = new SqlCommand();
// 2. 绑定
cmd.CommandText = deleteString;
// 3. 连接
cmd.Connection = conn;
// 4. 执行
cmd.ExecuteNonQuery();
}
finally
{
// 关闭
if (conn != null)
{
conn.Close();
}
}
}
public int GetNumberOfRecords() //统计
{
int count = -1;
try
{
conn.Open();
// 1. 初始化一个command
SqlCommand cmd = new SqlCommand("select count(*) from Categories", conn);
// 2. 执行
count = (int)cmd.ExecuteScalar();
}
finally
{
// 关闭
if (conn != null)
{
conn.Close();
}
}
return count;
}
}
采用SqlDataAdapter()的SqlCommandBuilder操作增,删,改,读,C#代码如下
private void UseCommandBuilder()
{
string connectionString = "Integrated Security=SSPI;Persist Security Info=False;Initial Catalog=Northwind;Data Source=LAP800";
SqlConnection connection = new SqlConnection(connectionString);
connection.Open();
try {
SqlCommand command = new SqlCommand("SELECT * FROM Customers", connection);
SqlDataAdapter adapter = new SqlDataAdapter(command);
SqlCommandBuilder builder = new SqlCommandBuilder(adapter);
Console.WriteLine(builder.GetInsertCommand().CommandText);
Console.WriteLine(builder.GetUpdateCommand().CommandText);
Console.WriteLine(builder.GetDeleteCommand().CommandText);
DataTable table = new DataTable();
adapter.Fill(table); //读出数据,平常用时会Fill给一个dataset,
DataRow row = table.NewRow;
row("CustomerID") = "PAULK";
row("CompanyName") = "Pauly's Edibles";
row("ContactName") = "Paul Kimmel";
row("ContactTitle") = "The Fat Man";
table.Rows.Add(row); //插入上面生成的一条数据
DataRow[] results = table.Select("CustomerID = 'ALFKI'");
results(0)("Region") = "DE"; //修改数据
DataRow[] deleteThese = table.Select("CustomerID = 'FARLA'");
foreach (int row in deleteThese) {
row.Delete(); //删除数据
}
adapter.Update(table);
table.AcceptChanges();
} catch (Exception ex) {
Debug.WriteLine(ex.Message);
throw;
} finally {
connection.Close();
}
收集
System.Data.SqlClient.SqlConnection 常用的一些连接字符串(C#代码)：
SqlConnection conn = new SqlConnection("Server=(local);Integrated Security=SSPI;database=Pubs");
SqlConnection conn = new SqlConnection("server=(local)\\NetSDK;database=pubs;Integrated Security=SSPI");
SqlConnection conn = new SqlConnection("Data Source=localhost;Integrated Security=SSPI;Initial Catalog=Northwind;");
SqlConnection conn = new SqlConnection(" data source=(local);initial catalog=xr;integrated security=SSPI;persist security info=False;workstation id=XURUI;packet size=4096; ");
SqlConnection conn = new System.Data.SqlClient.SqlConnection("Persist Security Info=False;Integrated Security=SSPI;database=northwind;server=mySQLServer");
SqlConnection conn = new SqlConnection( " uid=sa;pwd=passwords;initial catalog=pubs;data source=127.0.0.1;Connect Timeout=900");
System.Data.OleDb.OleDbConnection常用的一些连接字符串(C#代码)：
OleDbConnection conn = new OleDbConnection(@"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=D:\MyWeb\81\05\GrocerToGo.mdb");
OleDbConnection conn = new OleDbConnection(@"Provider=Microsoft.Jet.OLEDB.4.0;Password=;User ID=Admin;Data Source=grocertogo.mdb;");
OleDbConnection conn = new OleDbConnection("Provider=MSDAORA; Data Source=ORACLE8i7;Persist Security Info=False;Integrated Security=yes");
OleDbConnection conn = new OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0; Data Source=c:\bin\LocalAccess40.mdb");
OleDbConnection conn = new OleDbConnection("Provider=SQLOLEDB;Data Source=MySQLServer;Integrated Security=SSPI");