[SQL Server] 使用者登入失敗原因2：ADO.NET 資料庫連線字串錯誤(SqlExpress比較特別 除IP還要加上\\SQLEXPRESS 如140.116.123.123\\SQLEXPRESS)

Reference：http://blog.roodo.com/zaknafein/archives/7156245.html

1.命名空間要加入

using System.Data.SqlClient;

2.重頭戲來了

SqlConnection conn = new SqlConnection("server=*name or IP;database=資料庫名稱;uid=使用者帳號;pwd=使用者名稱");

*SqlExpress比較特別　除IP還要加上\\SQLEXPRESS
如140.116.123.123\\SQLEXPRESS

conn.open();

SqlCommand s_com = new SqlCommand();
s_com.CommandText = "SQL語法"; //語法如 select * from table_xxx
s_com.Connection = conn;

SqlDataReader s_read = s_com.ExecuteReader();
while ( s_read.Read() ) // 迴圈會執行到沒有下一筆資料為止
{
textbox.Text +=s_read["欄位名稱"].ToString(); //這裡只是舉例，會將每次讀到的row的特定欄位值接在textbox後面
}

s_read.Close();
conn.Close();
//判斷是不是有符合條件的ROW可以用 if ( s_read.HASROWS )
//s_read.HASROWS會回傳true or false

整理：
new SqlConnection("連接字串");

SqlConnection.open();

new SqlCommand();

SqlCommand.commandtext = " ";
Sqlcommand.connection = " ";

new SqlDataReader();

while(sqlDataReader.read())
{}

SqlDataReader.close();
SqlConnection.close();

==================================

How to update a specific table ?

using System.Data.SqlClient;

sqlconnection conn = new sqlconnection() ;
conn.open();

sqlcommand cmd = new sqlcommand() ;cmd.connection = conn ;
cmd.commandtext = " Update table_name SET item = 'value' where item = 'value' " ;
cmd.ExecuteNonQuery() ;  //done

==================================== 

how to insert a new row into datagridview by yourself

datagridview_name.rows.add(string,string,string,string) *參數的數目跟你設定欄位數目有關

how to insert a new row into the Table

sqlconnection conn_insert = new sqlconnection();
conn_insert.open();

sqlcommand cmd_insert = new sqlcommand();
cmd_insert.commandtext = " Insert into table_name (xx,xx,xx) values ('yy','yy','yy') " ;
cmd_insert.connection = conn_insert ;

cmd.insert.ExecuteNonQuery() ;

conn_insert.closer() ; //done