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C#连接数据库-曾,删,改,查

时间：2021-07-01 10:21:17 帮助过：2人阅读 

  1.         <span style="color: #0000ff;">static</span> <span style="color: #0000ff;">void</span> Main(<span style="color: #0000ff;">string</span><span style="color: #000000;">[] args)
  2.         {
  3.             </span><span style="color: #008000;">//</span><span style="color: #008000;">SqlConnection conn = new SqlConnection();</span><span style="color: #008000;">//</span><span style="color: #008000;">实例化
  4.             </span><span style="color: #008000;">//</span><span style="color: #008000;">conn.ConnectionString = "server=.;database=mydb;uid=sa;pwd=123";</span><span style="color: #008000;">//</span><span style="color: #008000;">初始化-----可以用下面一条语句执行</span>
  5.             SqlConnection conn = <span style="color: #0000ff;">new</span> SqlConnection(<span style="color: #800000;">"</span><span style="color: #800000;">server=.;database=mydb;uid=sa;pwd=123</span><span style="color: #800000;">"</span><span style="color: #000000;">);
  6.             Console.WriteLine(conn.State);
  7.             conn.Open();</span><span style="color: #008000;">//</span><span style="color: #008000;">打开数据库连接</span>
  8. <span style="color: #000000;">            Console.WriteLine(conn.State);
  9.             conn.Close();</span><span style="color: #008000;">//</span><span style="color: #008000;">关闭数据库连接</span>
  10. <span style="color: #000000;">            Console.WriteLine(conn.State);
  11.            
  12.         }</span>

连接数据库并插入数据

  1.         <span style="color: #0000ff;">static</span> <span style="color: #0000ff;">void</span> Main(<span style="color: #0000ff;">string</span><span style="color: #000000;">[] args)
  2.         {
  3.             SqlConnection conn </span>= <span style="color: #0000ff;">new</span> SqlConnection(<span style="color: #800000;">"</span><span style="color: #800000;">server=.;database=mydb;uid=sa;pwd=123</span><span style="color: #800000;">"</span><span style="color: #000000;">);
  4.             conn.Open();
  5.             SqlCommand cmd </span>= <span style="color: #0000ff;">new</span><span style="color: #000000;"> SqlCommand();
  6.             cmd.Connection </span>= conn;<span style="color: #008000;">//</span><span style="color: #008000;">初始化,通过conn数据对象连接数据库</span>
  7.             cmd.CommandText = <span style="color: #800000;">"</span><span style="color: #800000;">insert into info values(‘p005‘,‘学生‘,‘0‘,‘n001‘,‘1990-02-1‘)</span><span style="color: #800000;">"</span>;<span style="color: #008000;">//</span><span style="color: #008000;">""内为SQL语句</span>
  8. <span style="color: #000000;">            cmd.ExecuteNonQuery();
  9.             conn.Close();
  10.             Console.WriteLine(</span><span style="color: #800000;">"</span><span style="color: #800000;">OK</span><span style="color: #800000;">"</span><span style="color: #000000;">);
  11.         }</span>

连接数据库并修改数据

  1.         <span style="color: #0000ff;">public</span> <span style="color: #0000ff;">static</span> <span style="color: #0000ff;">void</span> Main(<span style="color: #0000ff;">string</span><span style="color: #000000;">[] args)
  2.         {
  3.             SqlConnection conn </span>= <span style="color: #0000ff;">new</span> SqlConnection(<span style="color: #800000;">"</span><span style="color: #800000;">server=.;database=mydb;uid=sa;pwd=123</span><span style="color: #800000;">"</span><span style="color: #000000;">);
  4.             conn.Open();
  5.             SqlCommand cmd </span>= <span style="color: #0000ff;">new</span><span style="color: #000000;"> SqlCommand();
  6.             cmd.Connection </span>=<span style="color: #000000;"> conn;
  7.             cmd.CommandText </span>= <span style="color: #800000;">"</span><span style="color: #800000;">update info set name=‘学员‘ where code=‘p005‘</span><span style="color: #800000;">"</span><span style="color: #000000;">;
  8.             cmd.ExecuteNonQuery();
  9.             conn.Close();
  10.         }</span>

连接数据库并删除数据

  1. <span style="color: #0000ff;">        public</span> <span style="color: #0000ff;">static</span> <span style="color: #0000ff;">void</span> Main(<span style="color: #0000ff;">string</span><span style="color: #000000;">[] args)
  2.         {
  3.             SqlConnection conn </span>= <span style="color: #0000ff;">new</span> SqlConnection(<span style="color: #800000;">"</span><span style="color: #800000;">server=.;database=mydb;uid=sa;pwd=123</span><span style="color: #800000;">"</span><span style="color: #000000;">);                               
  4.             conn.Open();            
  5.             SqlCommand cmd </span>=<span style="color: #000000;"> conn.CreateCommand();
  6.             cmd.CommandText </span>= <span style="color: #800000;">"</span><span style="color: #800000;">delete from info where code=‘p005‘</span><span style="color: #800000;">"</span><span style="color: #000000;">;
  7.             cmd.ExecuteNonQuery();
  8.             conn.Close();           
  9.         }</span>

 

 连接数据库查询数据

  1.         <span style="color: #0000ff;">static</span> <span style="color: #0000ff;">void</span> Main(<span style="color: #0000ff;">string</span><span style="color: #000000;">[] args)
  2.         {
  3.             SqlConnection conn </span>= <span style="color: #0000ff;">new</span> SqlConnection(<span style="color: #800000;">"</span><span style="color: #800000;">server=.;database=mydb;uid=sa;pwd=123</span><span style="color: #800000;">"</span><span style="color: #000000;">);            
  4.             conn.Open();
  5.             SqlCommand cmd </span>=<span style="color: #000000;"> conn.CreateCommand();
  6.             cmd.CommandText </span>= <span style="color: #800000;">"</span><span style="color: #800000;">select * from info</span><span style="color: #800000;">"</span><span style="color: #000000;">;
  7.             SqlDataReader r </span>= cmd.ExecuteReader();<span style="color: #008000;">//</span><span style="color: #008000;">查询语句用ExecuteReader返回SqlDataReader类</span>
  8.             <span style="color: #0000ff;">while</span><span style="color: #000000;"> (r.Read())
  9.             {
  10.                 
  11.                 Console.WriteLine(r[</span><span style="color: #800080;">0</span>].ToString()+r[<span style="color: #800080;">1</span>].ToString()+r[<span style="color: #800080;">2</span><span style="color: #000000;">].ToString());
  12.             }
  13.             conn.Close();
  14.         }</span>

 

 

 案例:用户登录实现

  1.         <span style="color: #0000ff;">public</span> <span style="color: #0000ff;">static</span> <span style="color: #0000ff;">void</span> Main(<span style="color: #0000ff;">string</span><span style="color: #000000;">[] arges)
  2.         {
  3.             Console.Write(</span><span style="color: #800000;">"</span><span style="color: #800000;">用户名:</span><span style="color: #800000;">"</span><span style="color: #000000;">);
  4.             </span><span style="color: #0000ff;">string</span> uid =<span style="color: #000000;"> Console.ReadLine();
  5.             Console.Write(</span><span style="color: #800000;">"</span><span style="color: #800000;">密码:</span><span style="color: #800000;">"</span><span style="color: #000000;">);
  6.             </span><span style="color: #0000ff;">string</span> pwd =<span style="color: #000000;"> Console.ReadLine();
  7.             SqlConnection conn </span>= <span style="color: #0000ff;">new</span> SqlConnection(<span style="color: #800000;">"</span><span style="color: #800000;">server=.;database=mydb;uid=sa;pwd=123</span><span style="color: #800000;">"</span><span style="color: #000000;">);            
  8.             conn.Open();
  9.             SqlCommand cmd </span>=<span style="color: #000000;"> conn.CreateCommand();
  10.             cmd.CommandText </span>= <span style="color: #800000;">"</span><span style="color: #800000;">select * from login where username=‘</span><span style="color: #800000;">"</span>+uid+<span style="color: #800000;">"</span><span style="color: #800000;">‘ and password=‘</span><span style="color: #800000;">"</span>+pwd+<span style="color: #800000;">"</span><span style="color: #800000;">‘</span><span style="color: #800000;">"</span><span style="color: #000000;">;
  11.             SqlDataReader r </span>=<span style="color: #000000;"> cmd.ExecuteReader();
  12.             </span><span style="color: #0000ff;">if</span> (r.HasRows == <span style="color: #0000ff;">false</span><span style="color: #000000;">)
  13.             {
  14.                 Console.WriteLine(</span><span style="color: #800000;">"</span><span style="color: #800000;">嗯哼,不对</span><span style="color: #800000;">"</span><span style="color: #000000;">);
  15.             }
  16.             </span><span style="color: #0000ff;">else</span><span style="color: #000000;">
  17.             {
  18.                 Console.WriteLine(</span><span style="color: #800000;">"</span><span style="color: #800000;">嗯哼,正确</span><span style="color: #800000;">"</span><span style="color: #000000;">);
  19.             }
  20.             conn.Close();
  21.         }<br></span>

*** .HasRows()与.read()区别:HasRows只关系读数据库中的数据是否可行,而不执行读的操作.Read是执行读的操作看是否执行成功.二者都返回一个bool行的变量.***

C#连接数据库-曾,删,改,查

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