<connectionStrings>

    <add name="constr_name" connectionString="server=192.168.1.139;uid=sa;pwd=123456;Trusted_Connection=no;Database=dabasename" providerName="system.data.sqlclient"/>

</connectionStrings>
注：constr_name(自定义名)，server（sqlserver服务器地址），uid（登录名），pwd（密码），Trusted_Connection（是否使用windows账户登录），Database（数据库名），providerName（数据库类型，sqlserver的为system.data.sqlclient）-

//一、连接数据库

string connectionString = ConfigurationManager.ConnectionStrings["constr_name"].ToString();

SqlConnection conn = new SqlConnection(connectionString);

conn.Open();

//二、构建数据库操作类

SqlCommand command = new SqlCommand();

command.CommandText = "SELECT * FROM [User];";

command.Connection = conn;

//三、读取数据

SqlDataReader reader = command.ExecuteReader();

//四、将数据写入对象

User user = null;

List<User> list = new List<User>();

while (reader.Read())

{

    user = new User();

    user.id = (int)reader["id"];

    user.name = reader["name"].ToString();

    list.Add(user);

}

//五、关闭

reader.Close();

conn.Close();

//另外，User实体类

class User

{

public int id { get; set; }

public string name { get; set; }

}

int result = ;

//一、连接数据库

string connectionString = ConfigurationManager.ConnectionStrings["constr_name"].ToString();

SqlConnection conn = new SqlConnection(connectionString);

conn.Open();

//--开始事务

SqlTransaction trans = conn.BeginTransaction();

try

{

    //二、构建数据库操作类

    SqlCommand command = new SqlCommand();

    command.CommandText = "INSERT INTO [User] VALUES(1,'name1');";

    command.Connection = conn;

    command.Transaction = trans;//事务

    result += command.ExecuteNonQuery();//插入第一条用户数据并返回影响条数

    command.CommandText = "INSERT INTO [User] VALUES(2,'name2');";

    result += command.ExecuteNonQuery();//插入第二条用户数据并返回影响条数

    if (result == )

    {

        trans.Commit();//两条数据都插入成功则提交事务

    }

    else

    {

        trans.Rollback();//否则回滚事务，取消所有插入的数据

    }

}

catch (System.Exception ex)

{

    trans.Rollback();//出错,回滚事务

}

finally

{

    conn.Close();

}