Basic Database Operations Using C# - GeeksforGeeks

14 Sep, 2021
In this article, you are going to learn about how to perform basic database operations using system.data.SqlClient namespace in C#. The basic operations are INSERT, UPDATE, SELECT and DELETE. Although the target database system is SQL Server Database, the same techniques can be applied to other database systems because the query syntax used is standard SQL that is generally supported by all relational database systems.Prerequisites: Microsoft SQL Server Management StudioOpen Microsoft SQL Server Management Studio and write the below script to create a database and table in it. 
create database Demodb;

use Demodb;

CREATE TABLE demo(
    articleID varchar(30) NOT NULL PRIMARY KEY,
    articleName varchar(30) NOT NULL,
);

insert into demo values(1, 'C#');
insert into demo values(2, 'C++');
After executing the above script following table named demo is created and it contains the following data as shown in the screenshot. 
Connecting C# with Database: To work with a database, the first of all you required a connection. The connection to a database normally consists of the below-mentioned parameters. 
Database name or Data Source: The database name to which the connection needs to be set up and connection can be made or you can say only work with one database at a time.
Credentials: The username and password which needs to be used to establish a connection to the database.
Optional Parameters: For each database type, you can specify optional parameters to provide more information on how .NET should connect to the database to handle the data.
Note: Here, we are using command prompt to execute these codes. To see the result, you can use the Microsoft SQL Server Management Studio.Code 1#: Connecting with database in C# 
csharp
// C# code to connect the databaseusing System;using System.Data.SqlClient; namespace Database_Operation { class DBConn {     // Main Method    static void Main()    {        Connect();        Console.ReadKey();    }     static void Connect()    {        string constr;         // for the connection to        // sql server database        SqlConnection conn;         // Data Source is the name of the        // server on which the database is stored.        // The Initial Catalog is used to specify        // the name of the database        // The UserID and Password are the credentials        // required to connect to the database.        constr = @"Data Source=DESKTOP-GP8F496;Initial Catalog=Demodb;User ID=sa;Password=24518300";         conn = new SqlConnection(constr);         // to open the connection        conn.Open();         Console.WriteLine("Connection Open!");           // to close the connection        conn.Close();    }}}
Output: 
Connection Open !
Code #2: Using Select Statement and SqlDataReader for accessing the data in C# 
csharp
// C# code to demonstrate how// to use select statementusing System;using System.Data.SqlClient; namespace Database_Operation { class SelectStatement{     // Main Method    static void Main()    {        Read();        Console.ReadKey();    }     static void Read()    {        string constr;         // for the connection to        // sql server database        SqlConnection conn;         // Data Source is the name of the        // server on which the database is stored.        // The Initial Catalog is used to specify        // the name of the database        // The UserID and Password are the credentials        // required to connect to the database.        constr = @"Data Source=DESKTOP-GP8F496;Initial Catalog=Demodb;User ID=sa;Password=24518300";         conn = new SqlConnection(constr);         // to open the connection        conn.Open();         // use to perform read and write        // operations in the database        SqlCommand cmd;         // use to read a row in        // table one by one        SqlDataReader dreader;         // to sore SQL command and        // the output of SQL command        string sql, output = "";          // use to fetch rows from demo table        sql = "Select articleID, articleName from demo";         // to execute the sql statement        cmd = new SqlCommand(sql, conn);         // fetch all the rows        // from the demo table        dreader = cmd.ExecuteReader();         // for one by one reading row        while (dreader.Read()) {            output = output + dreader.GetValue(0) + " - " +                                dreader.GetValue(1) + "\n";        }         // to display the output        Console.Write(output);         // to close all the objects        dreader.Close();        cmd.Dispose();        conn.Close();    }}}
Output: 
1 - C#
2 - C++
Code #3: Inserting the data into the database using Insert Statement in C# 
csharp
// C# code for how to use Insert Statementusing System;using System.Data.SqlClient;  namespace Database_Operation {     class InsertStatement {         // Main Method    static void Main()    {        Insert();        Console.ReadKey();    }      static void Insert()    {         string constr;          // for the connection to        // sql server database        SqlConnection conn;          // Data Source is the name of the        // server on which the database is stored.        // The Initial Catalog is used to specify        // the name of the database        // The UserID and Password are the credentials        // required to connect to the database.        constr = @"Data Source=DESKTOP-GP8F496;Initial Catalog=Demodb;User ID=sa;Password=24518300";          conn = new SqlConnection(constr);          // to open the connection        conn.Open();          // use to perform read and write        // operations in the database        SqlCommand cmd;                 // data adapter object is use to        // insert, update or delete commands        SqlDataAdapter adap = new SqlDataAdapter();                 string sql = "";                 // use the defined sql statement        // against our database        sql = "insert into demo values(3, 'Python')";                 // use to execute the sql command so we        // are passing query and connection object        cmd = new SqlCommand(sql, conn);                 // associate the insert SQL        // command to adapter object        adap.InsertCommand = new SqlCommand(sql, conn);                 // use to execute the DML statement against        // our database        adap.InsertCommand.ExecuteNonQuery();                 // closing all the objects        cmd.Dispose();        conn.Close();    }}}
Output: 
Code #4: Updating the data into the database using Update Statement in C# 
csharp
// C# code for how to use Update Statementusing System;using System.Data.SqlClient;  namespace Database_Operation {     class UpdateStatement {         // Main Method    static void Main()    {        Update();        Console.ReadKey();    }      static void Update()    {       string constr;           // for the connection to        // sql server database        SqlConnection conn;           // Data Source is the name of the        // server on which the database is stored.        // The Initial Catalog is used to specify        // the name of the database        // The UserID and Password are the credentials        // required to connect to the database.        constr = @"Data Source=DESKTOP-GP8F496;Initial Catalog=Demodb;User ID=sa;Password=24518300";           conn = new SqlConnection(constr);           // to open the connection        conn.Open();           // use to perform read and write        // operations in the database        SqlCommand cmd;                  // data adapter object is use to        // insert, update or delete commands        SqlDataAdapter adap = new SqlDataAdapter();                  string sql = "";                 // use the define sql        // statement against our database        sql = "update demo set articleName='django' where articleID=3";                 // use to execute the sql command so we        // are passing query and connection object        cmd = new SqlCommand(sql, conn);                 // associate the insert SQL        // command to adapter object        adap.InsertCommand = new SqlCommand(sql, conn);                 // use to execute the DML statement against        // our database        adap.InsertCommand.ExecuteNonQuery();                 // closing all the objects        cmd.Dispose();        conn.Close();    }}}
Output: 
Code #5: Deleting the data into the database using Delete Statement in C# 
csharp
// C# code for how to use Delete Statementusing System;using System.Data.SqlClient;  namespace Database_Operation {     class DeleteStatement {         // Main Method    static void Main()    {        Delete();        Console.ReadKey();    }      static void Delete()    {       string constr;           // for the connection to        // sql server database        SqlConnection conn;           // Data Source is the name of the        // server on which the database is stored.        // The Initial Catalog is used to specify        // the name of the database        // The UserID and Password are the credentials        // required to connect to the database.        constr = @"Data Source=DESKTOP-GP8F496;Initial Catalog=Demodb;User ID=sa;Password=24518300";           conn = new SqlConnection(constr);           // to open the connection        conn.Open();           // use to perform read and write        // operations in the database        SqlCommand cmd;                  // data adapter object is use to        // insert, update or delete commands        SqlDataAdapter adap = new SqlDataAdapter();                  string sql = "";                 // use the define SQL statement        // against our database        sql = "delete from demo where articleID=3";                 // use to execute the sql command so we        // are passing query and connection object        cmd = new SqlCommand(sql, conn);                 // associate the insert SQL        // command to adapter object        adap.InsertCommand = new SqlCommand(sql, conn);                 // use to execute the DML statement        // against our database        adap.InsertCommand.ExecuteNonQuery();                 // closing all the objects        cmd.Dispose();        conn.Close();    }}}
Output: 
 
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