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Friday, May 30, 2014

How to Use Filtered TextBox Extender of AJAX in ASP.NET

FilteredTextBoxExtender enables you to apply filtering to a text box control that prevents certain characters from being inserted in the text box. For example, you can limit a text box to either enter only characters, or digit, or dates. This extender is different from ASP.NET validation controls as it prevents the users from entering invalid characters.

Lets take an simple example

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default3.aspx.cs" Inherits="Default3" %>

 <%@ Register Assembly="AjaxControlToolkit" Namespace="AjaxControlToolkit" TagPrefix="asp" %>

 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

 <html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title></title>
</head>
<body>
    <form id="form1" runat="server">
    <asp:ScriptManager ID="ScriptManager1" runat="server">
    </asp:ScriptManager>
    <div>
    Enter Number only:
        <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
        <asp:Button ID="Button1" runat="server" Text="Button" />
        <asp:FilteredTextBoxExtender ID="FilteredTextBoxExtender1" runat="server" TargetControlID ="TextBox1" FilterType="Numbers">
        </asp:FilteredTextBoxExtender>
    </div>
    </form>
</body>
</html>

Code Generate the following Output

How to Use Filtered TextBox Extender of AJAX in ASP.NET

For Lower case Letter Only Set 
FilterType="LowercaseLetters"
For Upper Case Letter only
FilterType="UppercaseLetters"
For Upper and Number
FilterType="UppercaseLetters,Numbers"

Thursday, May 29, 2014

Nested Gridview Example in ASP.NET

A gridview with some items and another gridview structure

<form id="form1" runat="server">
    <div>
        <asp:GridView ID="GridView1" runat="server">
        <Columns>
        <asp:TemplateField>
        
        <ItemTemplate>
            <asp:TextBox ID="TextBox1" runat="server" Text ='<%# Eval("database field") %>' />
        
        </ItemTemplate>
         <ItemTemplate>
             <asp:GridView ID="GridView2" runat="server">
             <Columns>
             <asp:TemplateField>
                 
        <ItemTemplate>
            <asp:DropDownList ID="DropDownList1" runat="server">
            </asp:DropDownList>
        
        </ItemTemplate>
             
             </asp:TemplateField>
             
             </Columns>
             </asp:GridView>
        
        </ItemTemplate>
        
        
        </asp:TemplateField>
        
        </Columns>
        </asp:GridView>
    </div>
    </form>

Multiple Events call same event Handler in ASP.NET

In ASP.NET,  you can connect multiple Events with same event handler. If you thing about it, this types of code reduce space complexity as well as time complexity. If you use events with separate events handler then take more time. Like

<div>
    Both Event and methods name are same, both call to same handler.<br />
&nbsp;<asp:Button ID="Button1" runat="server" Text="First Button" 
            onclick="Button1_Click" /><br />
         <asp:Button ID="Button2" runat="server" Text="Second Button" onclick="Button1_Click" /><br />
        <asp:Label ID="Label1" runat="server" Text=""></asp:Label>
    </div>
In my previous article, we have already discussed about it, which is how to determine which web server control is raised.

Business Logic Code

 protected void Button1_Click(object sender, EventArgs e)
    {
        Button button = (Button)sender;
        Label1.Text = button.Text;
    }

Code generate the following output

Multiple Events call same event Handler in ASP.NET

Multiple Events call same event Handler in ASP.NET

Tuesday, May 27, 2014

How to Render HTML Controls in View: Asp.Net MVC

Asp.Net MVC provides a way to write simple programming syntaxes and HTML Helpers convert them in to HTML at runtime to be simply open the pages at client end. These provides generates html and return result as a string.

Like other web form controls in Asp.Net, HTML helpers are used to modify HTML, but HTML Helpers does not have an event model/ view state as web form controls have. Programmer can use these helpers by using built in HTML property of the view that are in System.Web.Mvc.Html namespace. We can create our own Html helpers or use built-in provided in the specified namespace.

HTML helpers have methods for creating forms, rendering partial views, performing input validation etc. Here are some mostly used html helpers:

HTML Links

These type of links are used to render an html link on the page, but in MVC they create a link to redirect on a particular action of the controller.
        @Html.ActionLink(“Text to Display”, “Action-name”)

The first parameter is used to specify the text to be displayed for user and second parameter is used to specify the action-name to which user will redirect after click.

HTML BeginForm

To place a form element on MVC, following syntax is used that will create an HTML form with some parameter values listed below.

@using (Html.BeginForm())
{
//Other Html Helpers to complete the form
}

 Parameters used 
  • ActionName: specify the name of action on which user will redirect
  • ControllerName: name of controller in which action has written
  • Route values: the values send as a parameter to action
  • FormMethod: Type of form whether HttpPost or HttpGet
  • Html attributes: used at run time like making readonly, applying css classes and more.

    ------------------------
Here are some standard html helpers used mostly when programming:

Understanding Attributes in Asp.Net MVC

Earlier article was about to handle browser request from the user and then invokes related controller and actions written for that particular URL. What is to be done after these requests can also be specified by the programmer in Asp.Net MVC, as this article will discuss.

Asp.Net MVC provides a way to use some extra features for actions and controller, these features are called Attributes and Filters. We have discusses about Required attribute in creating MVC View Model using required field validations.

The first and most attribute, MVC use by default is [Authorize] which specifies which action is to be executed by authenticated users only or it may be used for whole controller. The syntax for this authorize attribute is:

[Authorize]
Public ActionResult Profile()
{
return View();
}

 Now whenever an un-authorized user will try to get access of this profile action, it will redirect the request to login page or the page specified.

Attributes can also take parameters specified in their declaration, they may be positional or named. Positional parameter corresponds to attribute’s public constructor like the one specified below. It will change the name of this action profile to Details, as specified as the parameter.

[ActionName(“Details”)]
Public ActionResult Profile()
{ return View(); }

Named parameter correspond to public property or field of the respective attribute. For example authorize attribute have some named parameters like order, roles and users as written in following code:

[Authorize(Roles="Role1, Role2", Users="User1, User2")]
Public ActionResult Profile()
{ return View(); }

By specifying these named parameters, this profile action will only be accessed by the users having role "Role1" and "Role2". If we talk about the users, this action will only be accessed by only the person having username "User1" and "User2".
Attribute is a class which inherits from the abstract class System.Attribure. 
So we have to inherit from the same System.Attribute class to create our own attribute. Each attribute class (created by us) will must ends with the word "Attribute". E.g.
  • AuthorizeAttribute
  • RequiredAttribute
  • ActionNameAttribute
  • CustomizedAttribute
  • ValueCheckAttribute

Search Value using Non-Clustered index: SQL Server

Similar to the clustered index, a non-clustered index also contains the index also contains the index key values and the row locators that point to the storage location of the data in a table. However, in a non-clustered index, the physical order of the rows is not the same as the index order.

Non-clustered indexes are typically created on columns used in joins and the WHERE clause. These indexes can also be created on columns where the values are modified frequently. The SQL Server creates non-clustered indexes by default when the CREATE INDEX command is given. There can be as many as 249 non-clustered indexes per table.

The data in a non-clustered index is present in a random order, but the logical ordering is specified by the index. The data rows may be randomly spread throughout a table. The non-clustered index tree contains the index keys in a sorted order, with the leaf level of the index containing a pointer to the data page and the row number in the data page.
  • The SQL Server perform the following steps when it uses a non-clustered index to search for a value:
  • The SQL Server obtains the address of the root page from the sysindexes table.
  • The search value is compared with the key values on the root page.
  • The page with the highest key value less than or equal to the search value is found.
  • The page pointer is followed to the next lower level in the index.
  • Steps 3 and 4 are repeated until the data page is reached.
  • The rows are searched on the leaf page for the specified value. If a match is not found, the table contains no matching rows. If a match is found, the pointer is followed to the data page and row-ID in the table and requested row is retrieved. 
Search Value using Non-Clustered index: SQL Server

The figure displays a non-clustered index present on the Eid attribute o the Employee table. To search for any value, the SQL Server would start from the root page and move down the B-Tree until it reaches a leaf page that contains a pointer to the required record. It would then use this pointer to access the record in the table. For example, to search for the record containing Eid E006 by using the non-clustered index, the following steps would be performed by the SQL Server:

  • The SQL Server starts from page 603, which is the root page.
  • It searches for the highest key value on the page, the page with a key value less than or equal to the search value, that is, to the page containing the pointer to Eid E005.
  • The search continues from page 602.
  • Eid E005 is found and the search continues to page 203.
  • Page 203 is searched to find a pointer to the actual row. Page 203 is the last page, or the leaf page, of the index.
  • The search then moves to page 302 of the table to find the actual row.

In an index, more than one row can contain duplicate values. However, if you configure an index to contain unique values, the index will also contain unique values. Such an index is called a unique index. You can create a unique index on a columns that contain unique values, such as the primary key columns.
A unique index can be clustered or non-clustered depending on the nature of the column

Types of Indexes provided by SQL Server

As described in the earlier article indexes can be managed easily. The SQL Server allows you to create the following types of indexes:

Clustered Index

A clustered index is an index that sorts and stores the data rows in the table based on their key values. Therefore, the data is physically sorted in the table when a clustered index is defined on it. Only one clustered index can be created per table. Therefore, you should build the index on attributes that have a high percentage of unique values and are not modified often.

In a clustered index, data is stored at the leaf level of the B-Tree. The SQL Server performs the following steps when it uses a clustered index to search for a value:
  • The SQL Server obtains the address of the root page from the sysindexes table, which is a system table containing the details of all the indexes in the database.
  • The search value is compared with the key values on the root page.
  • The page with the highest key value less than or equal to the search value is found.
  • The page pointer is followed to the next lower level in the index.
  • Steps 3 and 4 are repeated until the data page is reached.
  • The rows of data are searched on the data page until the search value is found. If the search value is not found on the data page, no rows are returned by the query.
Consider the following figure where the rows of the Employee table are sorted according to the Eid attribute and stored in the table.
Types of Indexes provided by SQL Server

Working of a Clustered Index

The preceding figure displays a clustered index on the Employee table. To search for any record, the SQL Server would start at the root page. It would then move down the B-Tree and the data values would be found on the leaf pages of the B-Tree. For example, if the row containing Eid E006 was to be searched by using a clustered index (refer to the preceding figure), the SQL Server perform the following steps:
  • The SQL Server starts from page 603, the root page.
  • The SQL Server searches for the highest key value on the page, which is less than or equal to the search value. The result of this search is the page containing the pointer to Eid E005.
  • The search continues from page 602. There, Eid E005 is found and the search continues to page 203.
  • Page 203 is searched to find the required row.
A clustered index determines the order in which the rows are actually stored. Therefore, you can define only one clustered index on a table.
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