Difference Between DataReader, DataSet, DataAdapter and DataTable in C#

DataReader
DataReader is used to read the data from database and it is a read and forward only connection oriented architecture during fetch the data from database. DataReader will fetch the data very fast when compared with dataset. Generally we will use ExecuteReader object to bind data to datareader.
To bind DataReader data to GridView we need to write the code like as shown below:

Protected void BindGridview()

{

using (SqlConnection conn = new SqlConnection("Data Source=abc;Integrated Security=true;Initial Catalog=Test"))

{

con.Open();

SqlCommand cmd = new SqlCommand("Select UserName, First Name,LastName,Location FROM Users", conn);

SqlDataReader sdr = cmd.ExecuteReader();

gvUserInfo.DataSource = sdr;

gvUserInfo.DataBind();

conn.Close();

}

}

• Holds the connection open until you are finished (don't forget to close it!).
• Can typically only be iterated over once
• Is not as useful for updating back to the database

DataSet
DataSet is a disconnected orient architecture that means there is no need of active connections during work with datasets and it is a collection of DataTables and relations between tables. It is used to hold multiple tables with data. You can select data form tables, create views based on table and ask child rows over relations. Also DataSet provides you with rich features like saving data as XML and loading XML data.

protected void BindGridview()

{

    SqlConnection conn = new SqlConnection("Data Source=abc;Integrated Security=true;Initial Catalog=Test");

    conn.Open();

    SqlCommand cmd = new SqlCommand("Select UserName, First Name,LastName,Location FROM Users", conn);

    SqlDataAdapter sda = new SqlDataAdapter(cmd);

    DataSet ds = new DataSet();

    da.Fill(ds);

    gvUserInfo.DataSource = ds;

    gvUserInfo.DataBind();

}

DataAdapter
DataAdapter will acts as a Bridge between DataSet and database. This dataadapter object is used to read the data from database and bind that data to dataset. Dataadapter is a disconnected oriented architecture. Check below sample code to see how to use DataAdapter in code:

protected void BindGridview()

{

    SqlConnection con = new SqlConnection("Data Source=abc;Integrated Security=true;Initial Catalog=Test");

    conn.Open();

    SqlCommand cmd = new SqlCommand("Select UserName, First Name,LastName,Location FROM Users", conn);

    SqlDataAdapter sda = new SqlDataAdapter(cmd);

    DataSet ds = new DataSet();

    da.Fill(ds);

    gvUserInfo.DataSource = ds;

    gvUserInfo.DataBind();

}

• Lets you close the connection as soon it's done loading data, and may even close it for you automatically
• All of the results are available in memory
• You can iterate over it as many times as you need, or even look up a specific record by index
• Has some built-in faculties for updating back to the database.

DataTable 
DataTable represents a single table in the database. It has rows and columns. There is no much difference between dataset and datatable, dataset is simply the collection of datatables.

protected void BindGridview()

{

     SqlConnection con = new SqlConnection("Data Source=abc;Integrated Security=true;Initial Catalog=Test");

     conn.Open();

     SqlCommand cmd = new SqlCommand("Select UserName, First Name,LastName,Location FROM Users", conn);

     SqlDataAdapter sda = new SqlDataAdapter(cmd);

     DataTable dt = new DataTable();

     da.Fill(dt);

     gridview1.DataSource = dt;

     gvidview1.DataBind();

}



DataReader
===========
DataReader is like a forward only recordset. It fetches one row at a time so very less network cost compare to DataSet(Fethces all the rows at a time). DataReader is readonly so we can't do any transaction on them. DataReader will be the best choice where we need to show the data to the user which requires no transaction. As DataReader is forward only so we can't fetch data randomly. .NET Data Providers optimizes the datareader to handle huge amount of data.

DataSet
=======
DataSet is an in memory representation of a collection of Database objects including tables of a relational database schemas.
DataSet is always a bulky object that requires a lot of memory space compare to DataReader. We can say that the DataSet is a small database because it stores the schema and data in the application memory area. DataSet fetches all data from the datasource at a time to its memory area. So we can traverse through the object to get the required data like querying database.