Difference: DataSet, DataReader, DataAdapter, DataView in .NET

Now, here in this tutorial, I’ll explain the difference between DataSet, DataReader, DataAdapter and DataView in .net with examples.

1] DataSet:

Dataset is connection-less oriented, that means whenever we bind data from database it connects indirectly to the database and then disconnected. It has read/write access on data tables. It supports both forward and backward scanning of data.

DataSet is a container of one or more DataTable. More often than not, it will just contain one table, but if you do a query with multiple SELECT statements, the DataSet will contain a table for each.

You have to be careful about how much data you pull into a DataSet, because this is an in-memory representation. You can Fill a DataSet using the Fill() method of a DataAdapter.

For example code, you can download it at the end of this tutorial!

2] DataReader:

DataReader is connection-oriented, that means whenever we bind data from database it must require a connection and after that disconnected from the connection. It has read-only access, we can’t do any transaction on them. It supports forward-only scanning of data, in other words you can’t go backward.

DataReader fetches one row at a time so very less network cost as compare to DataSet(that fethces all the rows at a time). It is scalable to any number of records, at least in terms of memory pressure, since it only loads one record at a time. One typical way to get a DataReader is by using the ExecuteReader() method of a DbCommand.

For example code, you can download it at the end of this tutorial!

3] DataAdapter:

DataAdapter is an ADO.NET Data Provider. DataAdapter can perform any SQL operations like Insert, Update, Delete, Select in the Data Source by using SqlCommand to transmit changes back to the database.

DataAdapter provides the communication between the Dataset/DataTable and the Datasource. We can use the DataAdapter in combination with the DataSet/DataTable objects. These two objects combine to enable both data access and data manipulation capabilities.

For example code, you can download it at the end of this tutorial!

4] DataView:

Generally, we use DataView to filter and sort DataTable rows. So we can say that DataView is like a virtual subset of a DataTable. This capability allows you to have two controls bound to the same DataTable, but showing different versions of the data.

For example, one control may be bound to a DataView showing all of the rows in the table, while a second may be configured to display only the rows that have been deleted from the DataTable. The DataTable also has a DefaultView property which returns the default DataView for the table.

Server.MapPath

Server.MapPath specifies the relative or virtual path to map to a physical directory.

• Server.MapPath(".")1 returns the current physical directory of the file (e.g. aspx) being executed
• Server.MapPath("..") returns the parent directory
• Server.MapPath("~") returns the physical path to the root of the application
• Server.MapPath("/") returns the physical path to the root of the domain name (is not necessarily the same as the root of the application)

An example:

Let's say you pointed a web site application (http://www.example.com/) to

C:\Inetpub\wwwroot

and installed your shop application (sub web as virtual directory in IIS, marked as application) in

D:\WebApps\shop

For example, if you call Server.MapPath in following request:

http://www.example.com/shop/products/GetProduct.aspx?id=2342

then:

• Server.MapPath(".")1 returns D:\WebApps\shop\products
• Server.MapPath("..") returns D:\WebApps\shop
• Server.MapPath("~") returns D:\WebApps\shop
• Server.MapPath("/") returns C:\Inetpub\wwwroot
• Server.MapPath("/shop") returns D:\WebApps\shop

If Path starts with either a forward (/) or backward slash (\), the MapPath method returns a path as if Path were a full, virtual path.

If Path doesn't start with a slash, the MapPath method returns a path relative to the directory of the request being processed.

Note: in C#, @ is the verbatim literal string operator meaning that the string should be used "as is" and not be processed for escape sequences.

Footnotes

1. Server.MapPath(null) and Server.MapPath("") will produce this effect too.

Find and Replace Text in Text / HTML Files

public void ReplaceInFile(string filePath,string replaceText,string findText)
{
    try
    {
         System.IO.StreamReader objReader;
         objReader= new System.IO.StreamReader(filePath);
         string content= objReader.ReadToEnd();
         objReader.Close();
         content= Regex.Replace(content,findText,replaceText);
         StreamWriter writer= new StreamWriter(filePath);
         writer.Write(content);
         writer.Close();
    }
     catch(IOException iexp)
{
   throw;
}

Execute JavaScript function from ASP.NET codebehind

Calling a JavaScript function from codebehind is quiet simple, yet it confuses a lot of developers. Here's how to do it. Declare a JavaScript function in your code as shown below:
JavaScript

<head runat="server">
    <title>Call JavaScript From CodeBehind</title>
    <script type="text/javascript">
        function alertMe() {
            alert('Hello');
        }
    </script>
</head>

In order to call it from code behind, use the following code in your Page_Load
C#

protected void Page_Load(object sender, EventArgs e)
{
    if (!ClientScript.IsStartupScriptRegistered("alert"))
    {
        Page.ClientScript.RegisterStartupScript(this.GetType(),
            "alert", "alertMe();", true);
    }
}

Select DropDownList programmatically

Set by Text:

 DDL.SelectedIndex = DDL.Items.IndexOf(DDL.Items.FindByText("PassedValue"));

Set by Value: 

DDL.SelectedIndex = DDL.Items.IndexOf(DDL.Items.FindByValue("PassedValue"));

How to populate month name in DropDownList in ASP.NET

http://dotnetsqltips.blogspot.com/2012/01/how-to-populate-month-name-in.html

Get the ConnectionString from the Web.Config file with only one line of code (C#)

Get the ConnectionString from the Web.Config file with only one line of code (C#):

var conString = ConfigurationManager.ConnectionStrings["LocalSqlServer"];
string strConnString = conString.ConnectionString;