DataReader ADO.Net C# - Programming Example

In this tutorial, you will learn

1. What is DataReaders?
2. How to use DataReaders in ADO.NET for retrieving data?
3. Programming Examples

What is DataReaders?

The DataReader object in C# ADO.NET allows you to retrieve data from database in read-only and forward-only mode. It means you can only read and display data but can’t update or delete data. If you want to make modification in retrieved data you need to use DataAdapter instead of DataReader.

Why and When to Use DataReader?

When you want to only display information or search result, you can use DataReader. There are various advantages of using DataReader like:

1. The retrieved data is stored in the network buffer in the client and then the client can read data using Read method. As data gets stored in the client network buffer it increases application performance significantly.

2. By default DataReader stores only one row at a time in memory. It reduces system overhead.

Methods and Properties of DataReader

Properties

PROPERTY DESCRIPTION
Depth Indicates the depth of nesting for row
FieldCount Returns number of columns in a row
IsClosed Indicates whether a data reader is closed
Item Gets the value of a column in native format
RecordsAffected Number of row affected after a transaction

Methods

METHOD DESCRIPTION
Close Closes a DataRaeder object.
Read Reads next record in the data reader.
NextResult Advances the data reader to the next result during batch transactions.
Getxxx There are dozens of Getxxx methods. These methods read a specific data type value from a column. For example. GetChar will return a column value as a character and GetString as a string.

How to use DataReaders in ADO.NET for retrieving data?

 
using System;
using System.Data.SqlClient;

namespace DataReader_Examples
{
    class Program
    {
        static void Main(string[] args)
        {
            string ConString = @"Data Source=.\SQLEXPRESS;Initial Catalog=ComputerShop;Integrated Security=True";
            SqlConnection con = new SqlConnection(ConString);
            string querystring = "Select * from Items";
            try
            {
                con.Open();
                SqlCommand cmd = new SqlCommand(querystring, con);
                SqlDataReader reader = cmd.ExecuteReader();
                while (reader.Read())
                {
                    Console.WriteLine(reader[0].ToString() + " " + reader[1].ToString() + " " + reader[2].ToString());
                }
                
            }
            catch(SqlException ex)
            {
                Console.WriteLine(ex.ToString());
            }
            finally
            {
                con.Close();
                Console.ReadKey();
            }
        }
    }
}

Output

1 LED Screen $120 2 USB Keyboard $20 _

Summary

In this tutorial, you learned how to use DataReader in ADO.NET for accessing data from database table. In the next chapter, you will learn about DataAdapters and DataSets.

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