1.提取单条记录
//using System.Data;
//using System.Data.SqlClient;
 using (SqlConnection cn = new SqlConnection(%%1))
//ConfigurationManager.ConnectionStrings["db2ConnectionString"].ConnectionString
//Data Source=myServerAddress;Initial Catalog=myDataBase;User Id=myUsername;Password=myPassword;
      {
          SqlCommand cmd = new SqlCommand("Select Count(*) From jobs",cn);
          cn.Open();
%%2=cmd.ExecuteScalar(); //Message.InnerHtml
      }

2.单值比较
//using System.Data;
//using System.Data.SqlClient;
using (SqlConnection cn = new SqlConnection(%%1))
//ConfigurationManager.ConnectionStrings["db2ConnectionString"].ConnectionString
//Data Source=myServerAddress;Initial Catalog=myDataBase;User Id=myUsername;Password=myPassword;
      {
          SqlCommand cmd = new SqlCommand("Select Count(*) From jobs",cn);
          cn.Open();
%%2=cmd.ExecuteScalar(); //Message.InnerHtml
if(%%2==%%3)
{
%%4
}
      }

3.显示表格
//using System.Data;
//using System.Data.SqlClient;
DataSet ds=null;
using (SqlConnection cn = new SqlConnection(%%1))
//ConfigurationManager.ConnectionStrings["db2ConnectionString"].ConnectionString
//Data Source=myServerAddress;Initial Catalog=myDataBase;User Id=myUsername;Password=myPassword;
      {
          cn.Open();
cmd=new SqlDataAdapter("Select * From Author",cn);
ds=new DataSet();
cmd.Fill(ds,%%2); //"作者"
MyDataGrid.DataSource=ds.Tables(%%2).DefaultView; //"作者"
MyDataGrid.DataBind();
      }

4.操作表格
//using System.Data;
//using System.Data.SqlClient;
using (SqlConnection cn = new SqlConnection(%%1))
//ConfigurationManager.ConnectionStrings["db2ConnectionString"].ConnectionString
//Data Source=myServerAddress;Initial Catalog=myDataBase;User Id=myUsername;Password=myPassword;
      {
          cn.Open();
cmd=new SqlDataAdapter("Select * From Author",cn);
ds=new DataSet();
cmd.Fill(ds,%%2); //"作者"
MyDataGrid.DataSource=ds.Tables(%%2).DefaultView; //"作者"
MyDataGrid.DataBind();
      }

5.数值范围查询
//using System.Data;
//using System.Data.SqlClient;
using (SqlConnection cn = new SqlConnection(%%1))
//ConfigurationManager.ConnectionStrings["db2ConnectionString"].ConnectionString
//Data Source=myServerAddress;Initial Catalog=myDataBase;User Id=myUsername;Password=myPassword;
      {
 cn.Open();
int min = Int32.Parse(jcb1.selectedItem);
int max = Int32.Parse(jcb2.selectedItem);
cmd=new SqlDataAdapter("Select count(*) as pro_count From ProPrice where price between "
+ min + " and " + max,cn);
ds=new DataSet();
cmd.Fill(ds,%%2); //"作者"
MyDataGrid.DataSource=ds.Tables(%%2).DefaultView; //"作者"
MyDataGrid.DataBind();
      }

6.关闭时断开连接
//using System.Data;
//using System.Data.SqlClient;
using (SqlConnection cn = new SqlConnection(%%1))
//ConfigurationManager.ConnectionStrings["db2ConnectionString"].ConnectionString
//Data Source=myServerAddress;Initial Catalog=myDataBase;User Id=myUsername;Password=myPassword;
      {
      }

7.执行命令
//using System.Data;
//using System.Data.SqlClient;
using (SqlConnection cn = new SqlConnection(%%1))
//ConfigurationManager.ConnectionStrings["db2ConnectionString"].ConnectionString
//Data Source=myServerAddress;Initial Catalog=myDataBase;User Id=myUsername;Password=myPassword;
      {
          SqlCommand cmd = new SqlCommand("insert userRegister_t values('" 
              + TextBox1.Text + "','" + TextBox2.Text + "')",cn);
          cn.Open();
          cmd.ExecuteNonQuery();
      }

7.Oracle8/8i/9i数据库（thin模式）
//using System.Data;
Oracle Set Your custom connection strings values  

ODBC 
New version 
  
Driver={Microsoft ODBC for Oracle};Server=myServerAddress;Uid=myUsername;Pwd=myPassword; 

  
Old version 
  
Driver={Microsoft ODBC Driver for Oracle};ConnectString=OracleServer.world;Uid=myUsername;Pwd=myPassword; 


OLE DB, OleDbConnection (.NET) 
Standard security 
This connection string uses a provider from Microsoft.  
Provider=msdaora;Data Source=MyOracleDB;User Id=myUsername;Password=myPassword; 

  
Standard Security 
This connection string uses a provider from Oracle.  
Provider=OraOLEDB.Oracle;Data Source=MyOracleDB;User Id=myUsername;Password=myPassword; 

  
Trusted Connection 
  
Provider=OraOLEDB.Oracle;Data Source=MyOracleDB;OSAuthent=1; 

  
OracleConnection (.NET) 
Standard 
  
Data Source=MyOracleDB;Integrated Security=yes; 

This one works only with Oracle 8i release 3 or later  
  
Specifying username and password 
  
Data Source=MyOracleDB;User Id=myUsername;Password=myPassword;Integrated Security=no; 

This one works only with Oracle 8i release 3 or later  
Missing the System.Data.OracleClient namespace? Download .NET Managed Provider for Oracle >> 
Great article! "Features of Oracle Data Provider for .NET" by Rama Mohan G. at C# Corner >> 
  
Omiting tnsnames.ora 
This is another type of Oracle connection string that doesn't rely on you to have a DSN for the connection. You create a connection string based on the format used in the tnsnames.ora file without the need to actually have one of these files on the client pc.  
SERVER=(DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=MyHost)(PORT=MyPort))(CONNECT_DATA=(SERVICE_NAME=MyOracleSID)));uid=myUsername;pwd=myPassword; 

  
Core Labs OraDirect (.NET) 
Standard 
  
User ID=myUsername;Password=myPassword;Host=ora;Pooling=true;Min Pool Size=0;Max Pool Size=100;Connection Lifetime=0; 

Read more at Core Lab >> 
And at the product page >> 
  
Data Shape 
MS Data Shape 
  
Provider=MSDataShape.1;Persist Security Info=False;Data Provider=MSDAORA;Data Source=orac;User Id=myUsername;Password=myPassword; 

8.DB2数据库
string connString ="Server=myAddress:myPortNumber;Database=myDataBase;UID=myUsername;PWD=myPassword;";

9.SQL Server7.0/2000数据库
string connString ="Data Source=myServerAddress;Initial Catalog=myDataBase;User Id=myUsername;Password=myPassword;";
/*
Server=myServerAddress;Database=myDataBase;User ID=myUsername;Password=myPassword;Trusted_Connection=False;
*/
SQL Server2005数据库
string connString ="Data Source=myServerAddress;Initial Catalog=myDataBase;User Id=myUsername;Password=myPassword";
/*
Server=myServerAddress;Database=myDataBase;User ID=myUsername;Password=myPassword;Trusted_Connection=False;
*/

10.Sybase数据库
string connString ="Data Source='myASEserver';Port=5000;Database=myDataBase;Uid=myUsername;Pwd=myPassword;"; //Sybase Adaptive Server Enterprise
string connString ="Data Source=\\myserver\myvolume\mypat\mydd.add;User ID=myUsername;Password=myPassword;ServerType=REMOTE;"; //Sybase Advantage Database Server

11.Informix数据库
string connString ="Database=myDataBase;Host=192.168.10.10;Server=db_engine_tcp;Service=1492; Protocol=onsoctcp;UID=myUsername;Password=myPassword;";

12.MySQL数据库
string connString ="Server=myServerAddress;Database=myDataBase;Uid=myUsername;Pwd=myPassword;";

13.PostgreSQL数据库
string connString ="User ID=root;Password=myPassword;Host=localhost;Port=5432;Database=myDataBase; Pooling=true;Min Pool Size=0;Max Pool Size=100;Connection Lifetime=0;";

14.连接access数据库
string connString ="Provider=Microsoft.Jet.OLEDB.4.0;Data Source=C:\mydatabase.mdb;User Id=admin;Password=;";

15.连接MySql数据库
string connString ="Server=myServerAddress;Database=myDataBase;Uid=myUsername;Pwd=myPassword;";

16.程序计时
    DateTime runTime = Convert.ToDateTime(System.Configuration.ConfigurationSettings.AppSettings["TimerRunAt"]); 
    //运行时间 
    TimeSpan runTime = new TimeSpan(runTime.Ticks); 
    //现在时间 
    TimeSpan timeNow = new TimeSpan(DateTime.Now.Ticks);
    //时间间隔 
    TimeSpan ts = runTime.Subtract(timeNow); 
    //如果运行时间与当前时间的差大于0，则任务执行时间为当日 
    if(ts.TotalMilliseconds > 0)  
    { 
        return ts.TotalMilliseconds; 
    }
    //如果运行时间与当前时间的差小于0，则任务执行时间为次日
    Else 
    { 
        //差值的绝对值应加1天 
        return ts.Duration().Add(new TimeSpan(1,0,0,0,0)).TotalMilliseconds;
    } 

17.延时
//using System.Threading;
Thread.Sleep(Int32.Parse(%%1));

18.连接Excel文件
string connString = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + excel文件名（绝对路径） +";Extended Properties=Excel 8.0;";

19.GDI+时钟
/*
using System.Data; 
using System.Drawing; 
using System.Drawing.Drawing2D; 
*/
        private Point mickeyMouse = new Point(0, 0);
        private void Form1_Paint(object sender, PaintEventArgs e) 
        { 
            DrawClock(e.Graphics); 
            timer1.Start(); 
        } 

        private void DrawClock(Graphics g) 
        { 
            ///centre(120, 130);
            Rectangle outRect = new Rectangle(0, 0, 240, 260); 
            Rectangle midRect = new Rectangle(7, 7, 226, 246); 
            Rectangle inRect = new Rectangle(10, 10, 220, 240); 
 
            LinearGradientBrush outlBlueBrush = new LinearGradientBrush(outRect, Color.FromArgb(0, 0, 100), 
                Color.FromArgb(0, 0, 255), LinearGradientMode.BackwardDiagonal); 
            LinearGradientBrush midlBlueBrush = new LinearGradientBrush(midRect, Color.FromArgb(0, 0, 255), 
                Color.FromArgb(0, 0, 100), LinearGradientMode.BackwardDiagonal); 
            LinearGradientBrush inlBlueBrush = new LinearGradientBrush(inRect, Color.FromArgb(0, 0, 100), 
               Color.FromArgb(0, 0, 255), LinearGradientMode.BackwardDiagonal); 
 
            g.FillEllipse(outlBlueBrush, outRect); 
            g.FillEllipse(midlBlueBrush, midRect); 
            g.FillEllipse(inlBlueBrush, inRect); 
 
            outlBlueBrush.Dispose(); 
            midlBlueBrush.Dispose(); 
            inlBlueBrush.Dispose(); 
 
            //
            Font myFont = new Font("Arial", 20, FontStyle.Bold); 
            SolidBrush whiteBrush = new SolidBrush(Color.White); 
            g.DrawString("12", myFont, whiteBrush, 100, 10); 
            g.DrawString("6", myFont, whiteBrush, 110, 223); 
            g.DrawString("3", myFont, whiteBrush, 210, 120); 
            g.DrawString("9", myFont, whiteBrush, 10, 120); 
            g.DrawString("1", myFont, whiteBrush, 160, 26); 
            g.DrawString("2", myFont, whiteBrush, 194, 64); 
            g.DrawString("5", myFont, whiteBrush, 156, 210); 
            g.DrawString("4", myFont, whiteBrush, 192, 174); 
            g.DrawString("11", myFont, whiteBrush, 55, 28); 
            g.DrawString("10", myFont, whiteBrush, 22, 66); 
            g.DrawString("7", myFont, whiteBrush, 64, 210); 
            g.DrawString("8", myFont, whiteBrush, 28, 174); 
 
            myFont.Dispose(); 
            whiteBrush.Dispose(); 
            //DateTime; 
            g.TranslateTransform(120, 130, MatrixOrder.Append); 
 
            //
            Pen hourPen = new Pen(Color.White, 6); 
            hourPen.SetLineCap(LineCap.RoundAnchor, LineCap.ArrowAnchor, DashCap.Flat); 
            Pen minutePen = new Pen(Color.White, 4); 
            minutePen.SetLineCap(LineCap.RoundAnchor, LineCap.ArrowAnchor, DashCap.Flat); 
            Pen secondPen = new Pen(Color.Red, 2); 
 
            int sec = DateTime.Now.Second; 
            int min = DateTime.Now.Minute; 
            int hour = DateTime.Now.Hour; 
 
            double secondAngle = 2.0 * Math.PI * sec / 60.0; 
            double minuteAngle = 2.0 * Math.PI * (min + sec / 60.0) / 60.0; 
            double hourAngle = 2.0 * Math.PI * (hour + min / 60.0) / 12.0; 
 
            Point centre = new Point(0, 0); 
 
            Point hourHand = new Point((int)(40 * Math.Sin(hourAngle)), 
            (int)(-40 * Math.Cos(hourAngle))); 
            g.DrawLine(hourPen, centre, hourHand); 
 
            Point minHand = new Point((int)(80 * Math.Sin(minuteAngle)), 
            (int)(-80 * Math.Cos(minuteAngle))); 
            g.DrawLine(minutePen, centre, minHand); 
 
            Point secHand = new Point((int)(80 * Math.Sin(secondAngle)), 
            (int)(-80 * Math.Cos(secondAngle))); 
            g.DrawLine(secondPen, centre, secHand); 
 
            hourPen.Dispose(); 
            minutePen.Dispose(); 
            secondPen.Dispose(); 
        } 
 
        private void timer1_Tick(object sender, EventArgs e) 
        { 
            this.Invalidate();              
        } 

        private void hideToolStripMenuItem_Click(object sender, EventArgs e) 
        { 
            if (contextMenuStrip1.Items[0].ToString() == "Hide") 
            { 
                this.Hide(); 
                contextMenuStrip1.Items[0].Text = "Show"; 
                return; 
            } 
 
            if (contextMenuStrip1.Items[0].ToString() == "Show") 
            { 
                this.Show(); 
                contextMenuStrip1.Items[0].Text = "Hide"; 
                return; 
            } 
        } 
 
        private void Form1_MouseDown(object sender, MouseEventArgs e) 
        { 
            mickeyMouse = new Point(-e.X, -e.Y); 
        } 
 
        private void Form1_MouseMove(object sender, MouseEventArgs e) 
        { 
            if (e.Button == MouseButtons.Left) 
            { 
                Point mousePos = Control.MousePosition; 
                mousePos.Offset(mickeyMouse.X, mickeyMouse.Y); 
                Location = mousePos; 
            } 
        } 
 
        private void notifyIcon1_DoubleClick(object sender, EventArgs e) 
        { 
            if (contextMenuStrip1.Items[0].ToString() == "Show") 
            { 
                this.Show(); 
                contextMenuStrip1.Items[0].Text = "Hide"; 
                return; 
            } 
        }