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How do I use executescalar in c#

Updated on June 13, 2016

1. Introduction

In this hub, I will show how do we use the SQLCommand to retrieve a single value from the SQL Server database. I am going to get a total number of records in the Employees table of the NotrhWnd database using the ExecuteScalar Method. This method is useful when we want to retrieve a single value from the database and this method performs faster as it was designed to retrieve a single value. Have a look at the below Picture:

Ado.Net ExecuteScalar
Ado.Net ExecuteScalar | Source

The SQLConnection Object through ConnectionString knows where the database is located and how to connect to that. The SQLCommand object knows what needs to be executed on the database. The SQLCommand object uses the SQLConnection to execute the command stored in the CommandText property. The method ExecuteScalar returns the retrieved value as the Object.

The object will be converted to primitive data type using the C# way of type-casting techniques. OK let us jump to the coding part of the hub.

Console Project
Console Project | Source
//Sample 01: Required Name Space
using System.Data;
using System.Data.SqlClient;

As we are going to work on accessing the database, we need to have the above using statement for ease of use.

2) Inside the main function, a connection string is formed. Once the connection string is in place, it is easy to create the SqlConnection object. The Open method of the SqlConnection object is used to establish the connection to the SQL server database. Below is the code that opens the SQL Server database connection:

//Sample 02: Form the SQL Connection String and Open Connection Object.
string connection_string = "Data Source=(Local);Initial Catalog=Northwind;" +
"Persist Security Info=True;User ID=sa;Password=type_your_password_here";
SqlConnection con = new SqlConnection(connection_string);
con.Open();

Forming the Connection String is the Key to connect to the database. In the above connection string, (Local) represents that the database is running on the same system in which the program is executing. NorthWnd is the database name. Also, note that you should provide user id and password as part of the connection string.


Parts OfSQL Server DB  Connection String
Parts OfSQL Server DB Connection String | Source

3) Now SqlConnection object is ready. Once the connection is ready, a command object will be prepared to issue the Database command through the SqlConnection object. In the below-given code, once the SqlCommand object “cmd” is created, the CommandText property is set with the SQL statement that retrieves a single value from the database. Note that the SqlConnection object also given to this cmd object.

//Sample 03: Create the SQL Command Object
SqlCommand cmd = new SqlCommand();
cmd.CommandText = "Select Count(*) as Cnt from Employees";
cmd.Connection = con;

4) Now we have a valid SqlCommand, which knows what to execute through CommandText property and where to execute through the Connection property. Making a call to the function ExecuteScalar will return an object. As Count(*) returns an integer, we can typecast the object to Int32 using the System.Convert.ToInt32. Below is the code that retrieves the total number of records from the Employees table.

//Sample 04: Execute the Query and Get the Count of Emplyees
object count = cmd.ExecuteScalar();
Int32 Total_Records = System.Convert.ToInt32(count);

5) Finally the output is displayed in the console window. Below is the code:

//Sample 05: Print the Number of Records
System.Console.WriteLine("");
System.Console.WriteLine("Total Number of Records in Employees Table: {0}", Total_Records);
System.Console.WriteLine("");

3. Complete code and Output

Below is the complete code sample that shows retrieving the Total Number of employees from the Employees table of the NorthWnd Db:

using System;
using System.Collections.Generic;
using System.Text;
//Sample 01: Required Name Space
using System.Data;
using System.Data.SqlClient;

namespace ExecuteNonQuery
{
    class Program
    {
        static void Main(string[] args)
        {
            //Sample 02: Form the SQL Connection String and Open Connection Object.
            string connection_string = "Data Source=(Local);Initial Catalog=Northwind;" +
            "Persist Security Info=True;User ID=sa;Password=rohith";
            SqlConnection con = new SqlConnection(connection_string);
            con.Open();

            //Sample 03: Create the SQL Command Object
            SqlCommand cmd = new SqlCommand();
            cmd.CommandText = "Select Count(*) as Cnt from Employees";
            cmd.Connection = con;

            //Sample 04: Execute the Query and Get the Count of Emplyees
            object count = cmd.ExecuteScalar();
            Int32 Total_Records = System.Convert.ToInt32(count);

            //Sample 05: Print the Number of Records
            System.Console.WriteLine("");
            System.Console.WriteLine("Total Number of Records in Employees Table: {0}", Total_Records);
            System.Console.WriteLine("");
        }
    }
}

Output

Program Output
Program Output | Source

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