How to Add and Remove Placeholder Text in a .NET TextBox?

Adding Placeholder Text to a Textbox

Utilizing placeholder text in textboxes is a common feature in web development and helps guide users by providing default prompts. To emulate this functionality in desktop applications, we can employ a combination of event handling and text manipulation.

In .NET, we can achieve this behavior by assigning a placeholder text to the 'Text' property of a Textbox element. To make it dynamic and only appear when the textbox is empty, we can implement the 'GotFocus' and 'LostFocus' events.

When the textbox gains focus, the 'GotFocus' event is triggered. In the event handler, check if the current text matches the placeholder text. If so, clear the text. This action effectively removes the placeholder text and allows the user to enter their own.

Conversely, when the textbox loses focus, the 'LostFocus' event occurs. In its event handler, check if the text is empty or consists only of whitespace. If that's the case, assign the placeholder text back to the textbox to restore the default prompt.

Here's an example code snippet to illustrate the concept:

using System;
using System.Drawing;
using System.Windows.Forms;

public class Form1 : Form
{
    private TextBox myTextBox;

    public Form1()
    {
        myTextBox = new TextBox();
        // Set the placeholder text
        myTextBox.Text = "Enter text here...";

        // Add event handlers for focus events
        myTextBox.GotFocus += TextBox_GotFocus;
        myTextBox.LostFocus += TextBox_LostFocus;

        Controls.Add(myTextBox);
    }

    private void TextBox_GotFocus(object sender, EventArgs e)
    {
        // Check if the text is placeholder text
        if (myTextBox.Text == "Enter text here...")
        {
            // Clear the text
            myTextBox.Text = "";
        }
    }

    private void TextBox_LostFocus(object sender, EventArgs e)
    {
        // Check if the text is empty or whitespace
        if (string.IsNullOrWhiteSpace(myTextBox.Text))
        {
            // Add the placeholder text back
            myTextBox.Text = "Enter text here...";
        }
    }
}

By implementing these event handlers, we can dynamically add and remove placeholder text from the textbox, providing a similar functionality to HTML5's placeholder attribute.

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