10 案例登录：
/// <summary>
/// 登录成功后清空errorTimes
/// </summary>
/// <param name="conStr"></param>
/// <param name="name"></param>
private static void ResetErrorTimes(string conStr, string name)
{
using (SqlConnection conn = new SqlConnection(conStr))
{
conn.Open();
using (SqlCommand cmd = conn.CreateCommand())
{
cmd.CommandText = "update T_user set errortimes=0 where name=@Name";
cmd.Parameters.Add(new SqlParameter("@Name", name));
cmd.ExecuteNonQuery();
}
}
}
/// <summary>
/// 登录错误后errortimes+1
/// </summary>
/// <param name="conStr"></param>
/// <param name="name"></param>
private static void IncErrorTimes(string conStr, string name)
{
using (SqlConnection conn = new SqlConnection(conStr))
{
conn.Open();
using (SqlCommand cmd = conn.CreateCommand())
{
cmd.CommandText = "update T_user set errortimes+=1 where name=@Name";
cmd.Parameters.Add(new SqlParameter("@Name", name));
cmd.ExecuteNonQuery();
}
}
}
/// <summary>
/// 登录三次错误后退出
/// </summary>
/// <param name="conStr"></param>
static void ThreeLogin(string conStr)
{
do
{
Console.WriteLine("用户名：");
string name = Console.ReadLine();
Console.WriteLine("密码：");
string pwd = Console.ReadLine();
int errortimes = 0;
using (SqlConnection conn = new SqlConnection(conStr))
{
conn.Open();
using (SqlCommand cmd = conn.CreateCommand())
{
cmd.CommandText = "select * from T_user where name=@Name ";
cmd.Parameters.Add("@Name", name);
using (SqlDataReader reader = cmd.ExecuteReader())
{
if (reader.Read())
{
errortimes = reader.GetInt32(reader.GetOrdinal("errortimes"));
if (errortimes >= 3)
{
Console.WriteLine("登录错误超过三次，不能再登录了");
break;
}
else
{
if (reader.GetString(reader.GetOrdinal("password")) == pwd)
{
Console.WriteLine("登录成功");
ResetErrorTimes(conStr, name);
break;
}
else
{
Console.WriteLine("登录失败！");
//reader.Close();//在连接没有关闭前不能有其他操作
//cmd.CommandText = "update T_user set errortimes+=1 where name=@Name";
//cmd.ExecuteNonQuery();
IncErrorTimes(conStr, name);
}
}
}
else
{
Console.WriteLine("用户不存在,请重新输入！");
}
}
}
}
} while (true);
}
11 导入导出数据：
/// <summary>
/// 插入数据到数据库中
/// </summary>
/// <param name="conStr"></param>
/// <param name="name"></param>
/// <param name="age"></param>
private static void InsertData(string conStr,string name,int age) {
using (SqlConnection conn=new SqlConnection(conStr))
{
conn.Open();
using (SqlCommand cmd=conn.CreateCommand())
{
cmd.CommandText = "insert into T_Person values(@Name,@Age)";
cmd.Parameters.Add("@Name",name);
cmd.Parameters.Add("@Age",age);
cmd.ExecuteNonQuery();
}
}
}
/// <summary>
/// 文件导入数据库
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void button1_Click(object sender, EventArgs e)
{
string conStr = @"Data Source=ZHANGLIANGSQLEXPRESS;Initial Catalog=MyDB;Integrated Security=True";
OpenFileDialog ofd=new OpenFileDialog();
if (ofd.ShowDialog()==DialogResult.OK)
{
using (FileStream filestream =File.OpenRead(ofd.FileName))
{
using (StreamReader reader=new StreamReader(filestream))
{
string lines = null;
while ((lines=reader.ReadLine())!=null)
{
string[] line = lines.Split('|');
string name = line[0];
int age = Convert.ToInt32(line[1]);
InsertData(conStr,name,age);
}
}
}
MessageBox.Show("导入数据成功！");
}
}
/// <summary>
/// 导出
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void button2_Click(object sender, EventArgs e)
{
using (SqlConnection conn = new SqlConnection(conStr))
{
conn.Open();
using (SqlCommand cmd = conn.CreateCommand())
{
cmd.CommandText = "select name,age from T_Person";
using (SqlDataReader reader = cmd.ExecuteReader())
{
SaveFileDialog sfd = new SaveFileDialog();
if (sfd.ShowDialog() == DialogResult.OK)
{
///StringBuilder sb = new StringBuilder();
while (reader.Read())
{
string name = reader.GetString(reader.GetOrdinal("name"));
int age = reader.GetInt32(reader.GetOrdinal("age"));
using (FileStream stream=new FileStream(sfd.FileName, FileMode.Append))
{
using (StreamWriter writer=new StreamWriter(stream,Encoding.Default))
{
writer.WriteLine(string.Format("{0}|{1}",name,age));
}
}
}
MessageBox.Show("写入数据成功！");
}
}
}
}
}