asp.net C # Operations Database Summary (1/2)

Studentnum and Studentname.
One, SQL statements:

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--create Database Demo Use Demo CREATE TABLE Student ( Studentnum char () primary key, Studentname varchar () NOT NULL )

INSERT into Student values (' 20041000010201 ', ' publicity ')
Second, code:
1. Introducing namespaces: Using System.Data.SqlClient;
2. Define connection string, connect object, Command object:
Private String ConnectionStr;
Private SqlConnection connection;
Private SqlCommand command;
3. Initialize the connection string in the constructor, connect the object, command object

(1) Initialization of the connection string:
Way ①connectionstr= "Server=localhost;uid=sa;pwd=123456;database=demo";
Way ②connectionstr= "server=127.0.0.1"; Integrade Security=sspi;database=demo ";
Where Sims is the name of the database that I want to connect to. (1) The UID and PWD are the logins and passwords of your login database
Note: This connection is connected to the local database, to connect to other machines in the LAN database, the way to ① the "server=localhost;" Instead, the IP of the server= database.

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//        Connection string: String connectionString = "Provider=Microsoft.Jet.OLEDB.4.0 ;D ata Source=product.mdb "; //        establishes the connection: OleDbConnection connection = new OleDbConnection ( connectionString); //        uses the OleDbCommand class to execute the SQL statement: //         OleDbCommand cmd = new OleDbCommand (sql, connection); //        connection. Open ();        //        cmd. ExecuteNonQuery ();         #endregion #region Connection string String Strcon = @ "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=d: Program book software C # program code Access database Operation Addresslist.mdb"; Absolute path String Strcon = @ "Provider=Microsoft.Jet.OLEDB.4.0;Data source=" +environment.currentdirectory+ "\addressList.mdb" ;

Relative path

(2) Initializing the Connection object
Connection = new SqlConnection (CONNECTIONSTR);
(3) Initialize Command object
Command =new SqlCommand ();
command. Connection =connection;
4. Manipulating data in a database
(1) Querying the data in the database
Method One:

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String Snum=tbstudentnum. Text. Trim (); String str = "SELECT * from Student where studentnum= '" + snum + "'"; command. CommandText =str; Connection. Open (); if (command. ExecuteScalar () = null) { MessageBox.Show ("The student number you entered does not exist!") "," error ", Messageboxbuttons.ok,messageboxicon.error); } Else { SqlDataReader SDR = command. ExecuteReader (); while (SDR. Read ()) { Tbstudentnum. Text = sdr["Studentnum"]. ToString (); Tbstudentname.text = sdr["Studentname"]. ToString (); } Sdr. Close (); } Connection. Close ();

Method Two:

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String Snum=tbstudentnum. Text. Trim (); String str = "SELECT * from Student where studentnum= '" + snum + "'"; command. CommandText =str; Connection. Open (); if (command. ExecuteScalar () = null) { MessageBox.Show ("The student number you entered does not exist!") "," error ", Messageboxbuttons.ok,messageboxicon.error); } Else { SqlDataAdapter SDA = new SqlDataAdapter (str,connection); DataSet ds = new DataSet (); Sda. Fill (ds, "Student"); DataTable dt = ds. tables["Student"]; Tbstudentnum.text = dt. rows[0]["Studentnum"]. ToString (); Tbstudentname.text = dt. rows[0]["Studentname"]. ToString (); } Connection. Close ();

(2) Adding data to the database
Method One:

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String snum = TBstudentnum.Text.Trim (); String sname = TBstudentname.Text.Trim (); if (Snum = = "" | | sname = "") { MessageBox.Show ("Student study number or name cannot be empty!") "," The mistake, MessageBoxButtons.OK, MESSAGEBOXICON.ERROR); } Else { String insertstr= "insert into Student values (' +snum +" ', ' "+sname + ')"; Command.commandtext = Insertstr; Connection. Open (); Command. ExecuteNonQuery (); MessageBox.Show ("Students add success!") "," The Hint, "MessageBoxButtons.OK, MessageBoxIcon.Information); Connection. Close (); }

Method Two:

The code is as follows

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String str = "SELECT * from Student"; String insertstr = "INSERT into Student values (' + Snum +" ', ' "+ sname + ')"; SqlDataAdapter SDA = new SqlDataAdapter (str, connection); DataSet ds = new DataSet (); Sda. Fill (ds, "Student"); DataTable dt = ds. tables["Student"]; DataRow dr = dt. NewRow (); dr["Studentnum"] = Snum; dr["studentname"] = sname; Dt. Rows.Add (DR); Sda. InsertCommand = new SqlCommand (insertstr, connection); Sda. Update (ds, "Student"); MessageBox.Show ("Students add success!") "," The Hint, "MessageBoxButtons.OK, MessageBoxIcon.Information);

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