Working With the SqlParameter Class in ADO.NET

Introduction

The SqlParameter class is found in the "System.Data.SqlClient" namespace. It is a class of a connected architecture of the .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 the 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 Datatypes 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 the maximum size of the value of the parameter.
Value: It is used for assigning or getting the 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.

Here are some related resources.