Get Extension from Path/URL

Most often, we will get requirement to extract extension of a link in C#. The below code does that easily.

string ext = System.IO.Path.GetExtension(@"F:\Articles\ASP.Net Tips\tips.doc");

or

string ext = System.IO.Path.GetExtension(@"http://www.codedigest.com/Articles/ASPNETAJAX/127_Tips_and_Tricks_-_ASPNet_AJAX_Applications.aspx");

Clearing input controls at a stretch in ASP.Net

There will be situations where we will develop an input form for bulk input processing. Obviously, these forms will have large number of input controls like textbox, dropdownlist, checkbox and radiobutton, etc. In such forms, we need to reset these control once the input is processed for the subsequent request. You can use the below code to reset the input controls at a stretch instead of clearing it one by one.

private void btnClear_Click(object sender, System.EventArgs e)

{

Control myForm = Page.FindControl("Form1");

        foreach (Control ctrl in myForm.Controls)

        {

            //Clears TextBox

            if (ctrl is System.Web.UI.WebControls.TextBox)

            {

                (ctrl as TextBox).Text = "";

            }

            //Clears DropDown Selection

            if (ctrl is System.Web.UI.WebControls.DropDownList)

            {

                (ctrl as DropDownList).ClearSelection();

            }

            //Clears ListBox Selection

            if (ctrl is System.Web.UI.WebControls.ListBox)

            {

                (ctrl as ListBox).ClearSelection();

            }

            //Clears CheckBox Selection

            if (ctrl is System.Web.UI.WebControls.CheckBox)

            {

                (ctrl as CheckBox).Checked = false;

            }

            //Clears RadioButton Selection

            if (ctrl is System.Web.UI.WebControls.RadioButtonList)

            {

                (ctrl as RadioButtonList).ClearSelection();

            }

            //Clears CheckBox Selection

            if (ctrl is System.Web.UI.WebControls.CheckBoxList)

            {

                (ctrl as CheckBoxList).ClearSelection();

            }

        }

}

Get Control Name in JavaScript

When we use masterpage in ASP.Net, it will append the ContentPlaceholderId with the ID of the controls that is inside the Content tag during HTML rendering. For example, when there is a textbox with ID “txtAccountNumber” it will be rendered as “ctl00_ContentPlaceHolder1_txtAccountNumber” to the client, where “ContentPlaceHolder1” is the ID of the Content Placeholder of the Master Page. This behaviour is again seen when we use user controls.

To access any control in JavaScript we use,

document.getElementById(' ID') ;

In our case, it will be similar to,

document.getElementById(' ctl00_ContentPlaceHolder1_txtAccountNumber ')

The above statement will lead to script error if we unknowingly change the ID of the ContentPlaceholder or move the control to different ContentPlaceholder in the Page. Hence, whenever ContentPlaceholder ID is changed we need to revisit all the Jscript code and change the corresponding ID’s. To prevent this rework, we can register a hidden control from code behind which in turn will hold the client ID of the control.

Page.RegisterHiddenField("hdnAccountNoTextID", txtAccountNumber.ClientID);

Now we can make use of this hidden variable to get the client ID of the textbox in Jscript.

//gets the Client ID of the txtAccountNumber textbox

    var AccountNoTextID = document.getElementById('hdnAccountNoTextID').value; //Access the txtAccountNumber textbox

    var AccountNoText = document.getElementById('hdnAccountNoTextID');

Thus, the changes in ID of the container controls will not affect our JavaScript codes.

Invoking an Event in ASPX Page from UserControl

Consider we have a button in a UserControl. For example, if we need to raise an event in aspx page for every button click in user control, we need to declare an event in user control which should be registered with the event handler in the aspx page. Refer the below code.

UserControl

<%@ Control Language="C#" AutoEventWireup="true" CodeFile="WebUserControl.ascx.cs" Inherits="WebUserControl" %>

<asp:Button ID="Button1" runat="server" Text="Button" OnClick="Button1_Click" />

UserControl CodeBehind

public partial class WebUserControl : System.Web.UI.UserControl

{

    public event EventHandler usrCtrlButtonClick;

    protected void Page_Load(object sender, EventArgs e)

    {

    }

    protected void Button1_Click(object sender, EventArgs e)

    {

        usrCtrlButtonClick.Invoke(this, new EventArgs());

    }

}

ASPX Page

 protected void Page_Load(object sender, EventArgs e)

    {

        this.WebUserControl1.usrCtrlButtonClick += new EventHandler(this.usrctrlButtonClick);

   }  

    protected void usrctrlButtonClick(object sender, EventArgs e)

    {

        Response.Write("From aspx page");

    }

Selecting/Highlighting the TextBox Value If Validation Fails

Consider we have a validation JavaScript method which checks for the validity of the data entered in a TextBox. When the validation fails, we will alert or display a error message to the user and call focus() method on the control to let the user know the control on the page. At times, we will require select or highlight the invalid data instead of returning the focus to the control. Refer the below figure.

This can be achieved by calling the select() method on the control. Refer the below code,

document.getElementById('txtAccountNumber').select();