Skip to main content

How to use ListBox SelectedIndexChanged event in asp.net c#

ListBox SelectedIndexChanged Event
ListBox is an asp.net list web server control that contains a list of selectable items. More than one item is visible in ListBox control. ListBox SelectionMode property determines whether multiple items in the ListBox are selectable at a time.

ListBox SelectedIndexChanged event occurs when the SelectedIndex property or the SelectedIndices collection has changed. ListBox SelectedIndex property gets or sets the zero-based index of the currently selected item. And SelectedIndices property gets a collection that contains the zero-based indexes of all currently selected items in ListBox.

For multiple selections, the ListBox SelectedIndices property returns a collection containing the indexes of all selected items. ListBox SelectedIndexChanged event works when we set the ListBox AutoPostBack property value to True and write an event handler for the OnSelectedIndexChanged property.

when a user changes the selection of an item in a single selection mode ListBox control then the SelectedIndexChanged event occurs and the page post to the web server automatically. This event also occurs when the user adds or removes an item from multiple selected items in a multi-selection mode ListBox control.

The following c# example source code demonstrates to us how can we use ListBox SelectedIndexChanged event in asp.net.
ListBoxOnSelectedIndexChanged.aspx

<%@ Page Language="C#" %>

<!DOCTYPE html>

<script runat="server">
    protected void ListBox1_SelectedIndexChanged(object sender, System.EventArgs e)
    {
        Label1.Text = "Your Favorite Color: " + ListBox1.SelectedItem.Text;
    }
</script>

<html xmlns="http://www.w3.org/1999/xhtml">
<head id="Head1" runat="server">
    <title>How to use SelectedIndexChanged event in ListBox</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <h2 style="color:Maroon">ListBox: OnSelectedIndexChanged</h2>
        <asp:Label 
             ID="Label1"
             runat="server"
             Font-Bold="true"
             ForeColor="SeaGreen"
             Font-Size="Large"
             >
        </asp:Label>
        <br /><br />
        <asp:Label 
             ID="Label2"
             runat="server"
             Font-Bold="true"
             ForeColor="DarkCyan"
             Text="Color List"
             >
        </asp:Label>
        <br />
        <asp:ListBox 
             ID="ListBox1"
             runat="server"
             AutoPostBack="true"
             OnSelectedIndexChanged="ListBox1_SelectedIndexChanged"
             BackColor="DarkCyan"
             ForeColor="AliceBlue"
             >
             <asp:ListItem>LawnGreen</asp:ListItem>
             <asp:ListItem>LightSalmon</asp:ListItem>
             <asp:ListItem>MediumBlue</asp:ListItem>
             <asp:ListItem>MediumOrchid</asp:ListItem>
             <asp:ListItem>Lavender</asp:ListItem>
        </asp:ListBox>
    </div>
    </form>
</body>
</html>
Labels:

Popular posts from this blog

Restricting Jetpack Compose TextField to Numeric Input Only

Jetpack Compose has revolutionized Android development with its declarative approach, enabling developers to build modern, responsive UIs more efficiently. Among the many components provided by Compose, TextField is a critical building block for user input. However, ensuring that a TextField accepts only numeric input can pose challenges, especially when considering edge cases like empty fields, invalid characters, or localization nuances. In this blog post, we'll explore how to restrict a Jetpack Compose TextField to numeric input only, discussing both basic and advanced implementations. Why Restricting Input Matters Restricting user input to numeric values is a common requirement in apps dealing with forms, payment entries, age verifications, or any data where only numbers are valid. Properly validating input at the UI level enhances user experience, reduces backend validation overhead, and minimizes errors during data processing. Compose provides the flexibility to implement ...
Read more

jetpack compose - TextField remove underline

Compose TextField Remove Underline The TextField is the text input widget of android jetpack compose library. TextField is an equivalent widget of the android view system’s EditText widget. TextField is used to enter and modify text. The following jetpack compose tutorial will demonstrate to us how we can remove (actually hide) the underline from a TextField widget in an android application. We have to apply a simple trick to remove (hide) the underline from the TextField. The TextField constructor’s ‘colors’ argument allows us to set or change colors for TextField’s various components such as text color, cursor color, label color, error color, background color, focused and unfocused indicator color, etc. Jetpack developers can pass a TextFieldDefaults.textFieldColors() function with arguments value for the TextField ‘colors’ argument. There are many arguments for this ‘TextFieldDefaults.textFieldColors()’function such as textColor, disabledTextColor, backgroundColor, cursorC...
Read more

jetpack compose - Image clickable

Compose Image Clickable The Image widget allows android developers to display an image object to the app user interface using the jetpack compose library. Android app developers can show image objects to the Image widget from various sources such as painter resources, vector resources, bitmap, etc. Image is a very essential component of the jetpack compose library. Android app developers can change many properties of an Image widget by its modifiers such as size, shape, etc. We also can specify the Image object scaling algorithm, content description, etc. But how can we set a click event to an Image widget in a jetpack compose application? There is no built-in property/parameter/argument to set up an onClick event directly to the Image widget. This android application development tutorial will demonstrate to us how we can add a click event to the Image widget and make it clickable. Click event of a widget allow app users to execute a task such as showing a toast message by cli...
Read more