黑马程序员+ADO.Net基础(中)

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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=ZHANGLIANG\SQLEXPRESS;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！");

}

}

}

}

}

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