Working with SQL Parameters

Introduction
The SqlParameter class is found in the "System.Data.SqlClient" namespace. It is a class of a connected architecture of .NET framework. It represents parameters. To work with the SqlParameter class we should have a database. In this example I am using a Database "student" which has a "student_detail" table. "RollNo", "Name" and "City" are column names. I will save and retrieve records using SqlParameter class.  Here is a list of important properties of the SqlParameter class which will be used in this example.

SqlDbType : It is used to set the Sql Server Data types for a given parameter.

ParameterName : It is used to specify a parameter name.
Direction : It is used for setting the direction of a SqlParameter. It is Input or Output or both (InputOutput).
Size : It is used to set maximum size of value of parameter.

Value : It is used for assigning or getting value of the parameter. 

Now, take a Windows Forms application in Visual Studio 2010. Take some UI Controls and arrange them as shown in the figure below.



Write the following code for saving a record into the database.
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Data.SqlClient;
namespace WorkWithSqlParameterClass
{
    public partial class Form1 : Form    {
        public Form1()
        {
            InitializeComponent();
        }
 
        SqlConnection conn;
        SqlCommand comm;
        string connstring = "database=student;server=.;user=sa;password=wintellect";
        
    private void btnsave_Click(object sender, EventArgs e)
        {
            conn = new SqlConnection(connstring);
            conn.Open();
 
            comm = new SqlCommand();
            comm.Connection = conn;
 
            //Creating instance of SqlParameter             SqlParameter PmtrRollNo = new SqlParameter();
            PmtrRollNo.ParameterName = "@rn";// Defining Name            PmtrRollNo.SqlDbType = SqlDbType.Int; // Defining DataType            PmtrRollNo.Direction = ParameterDirection.Input; // Setting the direction  
            //Creating instance of SqlParameter             SqlParameter PmtrName = new SqlParameter();
            PmtrName.ParameterName = "@nm";// Defining Name            PmtrName.SqlDbType = SqlDbType.VarChar; // Defining DataType            PmtrName.Direction = ParameterDirection.Input;// Setting the direction  
            //Creating instance of SqlParameter             SqlParameter PmtrCity = new SqlParameter();

            PmtrCity.ParameterName = "@ct"; // Defining Name            PmtrCity.SqlDbType = SqlDbType.VarChar; // Defining DataType            PmtrCity.Direction = ParameterDirection.Input;// Setting the direction  
            // Adding Parameter instances to sqlcommand 
            comm.Parameters.Add(PmtrRollNo);
            comm.Parameters.Add(PmtrName);
            comm.Parameters.Add(PmtrCity);
 
            // Setting values of Parameter  
            PmtrRollNo.Value = Convert.ToInt32(txtrollno.Text);
            PmtrName.Value = txtname.Text;
            PmtrCity.Value = txtcity.Text;
 
            comm.CommandText = "insert into student_detail values(@rn,@nm,@ct)";
 
            try            {
                comm.ExecuteNonQuery();
                MessageBox.Show("Saved");
            }
            catch (Exception)
            {
                MessageBox.Show("Not Saved");
            }
            finally            {
                conn.Close();
            }
        }
    }
}
 
 Run the application. 

Output


Fill in the form and click the "Save" button. The record will be saved to the Database and a message box will be displayed with a confirmation message.


Now we retrieve records from the database. Take another button and set its text property as "Show". Add the following code for the "Show" button.
 

private void btnshow_Click(object sender, EventArgs e)
        {
            conn = new SqlConnection(connstring);
            conn.Open();
 
            comm = new SqlCommand();
            comm.Connection = conn;
 
            //Creating instance of SqlParameter             SqlParameter PmtrRollNo = new SqlParameter();
            PmtrRollNo.ParameterName = "@rn";// Defining Name            PmtrRollNo.SqlDbType = SqlDbType.Int; // Defining DataType            PmtrRollNo.Direction = ParameterDirection.Input; // Setting the direction  
            //Creating instance of SqlParameter             SqlParameter PmtrName = new SqlParameter();
            PmtrName.ParameterName = "@nm";// Defining Name            PmtrName.SqlDbType = SqlDbType.VarChar; // Defining DataType            PmtrName.Size = 30;
            PmtrName.Direction = ParameterDirection.Output;// Setting the direction  
            //Creating instance of SqlParameter             SqlParameter PmtrCity = new SqlParameter("@ct", SqlDbType.VarChar, 20);
            PmtrCity.Direction = ParameterDirection.Output;// Setting the direction  
            // Adding Parameter instances to sqlcommand 
            comm.Parameters.Add(PmtrRollNo);
            comm.Parameters.Add(PmtrName);
            comm.Parameters.Add(PmtrCity);
 
            // Setting values of Parameter  
            PmtrRollNo.Value = Convert.ToInt32(txtrollno.Text);
            PmtrName.Value = txtname.Text;
            PmtrCity.Value = txtcity.Text;
 
            comm.CommandText = "select @nm=name,@ct=city from student_detail where rollno=@rn";
 
            try            {
                comm.ExecuteNonQuery();
                txtname.Text = PmtrName.Value.ToString();
                txtcity.Text = PmtrCity.Value.ToString();
                }
                catch (Exception)
                {
                    MessageBox.Show("Not Found");
                }
                finally                {
                    conn.Close();
                }
            }
        } 
  
Run the application.
Output


Enter a roll number and click the "Show" button. It will show all the related information of the student having the given roll number.

Source :  http://www.c-sharpcorner.com/UploadFile/718fc8/working-with-sqlparameter-class-in-ado-net/