ADO. NET 7-use the Command object to find database records --- ShinePans,

ADO. NET 7-use the Command object to find database records --- ShinePans,

Query the number of data in the data path:

Code:

Using System; using System. collections. generic; using System. data; using System. data. sqlClient; using System. linq; using System. text; using System. threading. tasks; namespace SQLTest {class Program {static void Main (string [] args) {// connect to the database string connection = "server = Pan Shang \ SQLEXPRESS; database = db_test; trusted_Connection = true "; SqlConnection SC = new SqlConnection (connection); SC. connectionString = connecti On; try {SC. Open (); // Open the database connection Console. WriteLine ("the database connection has been enabled! "); SqlCommand cmd = new SqlCommand (" SELECT count (*) FROM db_student ", SC); int I = (int) cmd. executeScalar (); // execute the command Console for searching records. writeLine ("A total of {0} pieces of data in the table", I. toString (); // START: 3. modify the database data code /////////////////////////////////// /// // * SqlCommand cmd = new SqlCommand ("UPDATE db_student SET student_grade = 99 where student_name = @ name ", SC); // create the SqlCommand object cmd. parameters. add ("@ name", SqlDb Type. VarChar). Value = "pan"; int I = cmd. ExecuteNonQuery (); if (I> 0) Console. WriteLine ("modified successfully! "); * // END: 3. modify the database data code /////////////////////////////////// /// // START: 1. delete the database record code segment //////////////////////////////////// //// // * string plain text = "delete from db_student WHERE student_name = @ name "; sqlCommand cmd = new SqlCommand (plain text, SC); cmd. parameters. add ("@ name", SqlDbType. varChar ). value = "pan"; int I = cmd. executeNonQuery (); if (I> 0) Console. writeLine ("the record is deleted successfully.! "); * // END: 1. delete the database record code segment //////////////////////////////////// /// // START: 2. add the recorded code //////////////////////////////////// //// // * SqlCommand cmd = new SqlCommand (); // create the SqlCommand object cmd. commandType = CommandType. text; // set the command to run the command cmd. connection = SC; // set the object property cmd. commandText = "insert into db_student (student_name, student_age, student_address, student_grade) VALUES (@ nam E, @ age, @ address, @ grade) "; // Add a parameter and assign the cmd value to the parameter. parameters. add ("@ name", SqlDbType. varChar, 10 ). value = "pan"; cmd. parameters. add ("@ age", SqlDbType. int ). value = 19; cmd. parameters. add ("@ address", SqlDbType. varChar ). value = "Wuhan"; cmd. parameters. add ("@ grade", SqlDbType. int ). value = 100; int I = cmd. executeNonQuery (); // execute the database add record command if (I> 0) Console. writeLine ("successfully added the record"); * // The console outputs the Add record // END: 2. code for adding a record /////// //////////////////////////////////////// /// //} Catch (Exception ex) {Console. writeLine ("Opening Database Error: {0}", ex. message);} finally {SC. close (); Console. writeLine ("the database connection is closed! ") ;}System. Console. ReadLine ();}}}

Running result:

Brief description of steps for ADONET to access the database

1. Introduce the namespace
2. Define the connection string
3. Define the connection object
4. Write SQL statements
5. Create a command object
6, try {} catch {} finally {}
7. Open the database connection
8. Create a DataReader object.
9. Read the query results of the DataReader object row by row.
0. Close the DataReader object.
11. Close the database connection.

Methods and jobs for connecting the three objects of ADONet to the database

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