How do I fill an empty textbox with default text?

How开发者_如何学C do I fill a textbox with text if it is empty? I am using VB.NET.

It looks like you're describing a cue banner, which is prompt text that is displayed in an empty textbox. As of Windows XP, this functionality is natively supported by the operating system. The effect achieved doing it this way is much more elegant than setting the default text yourself in the TextChanged event. It looks like this:

Setting this up is accomplished at the level of the Windows API by sending the textbox control an EM_SETCUEBANNER message. To use this from a .NET project, you will have to use P/Invoke.

Fortunately, most of the work has already been done for you. This sample project is a quick and painless way to add cue banner support to an existing project. Here's another sample, with a more complete explanation of the process.

If you don't want your application to depend on an external DLL, you can add the necessary code directly to your project. The simplest way is to subclass the existing TextBox control, and add the code to support cue banners there. See this answer for the code you'll need. If you have trouble converting it to VB.NET, try this tool.

You will probably want to handle the TextChanged event and set some default text if the text box is empty when the event is fired.

I don't have a VB.NET example, but the following C# should be too hard to understand:

public Form1()
{
    this.InitializeComponent();

    textBox1.Tag = "Default text";
    textBox1.Text = (string)textBox1.Tag;
    textBox1.TextChanged += new EventHandler(OnTextChanged);
}

void OnTextChanged(object sender, EventArgs e)
{
    var textbox = (TextBox)sender;

    if (string.IsNullOrEmpty(textbox.Text))
    {
        textbox.Text = (string)textbox.Tag;
    }
}

And the event handler can be reused for several text boxes.

EDIT: Here's pretty much the same in VB.NET

Sub New()
    ' This call is required by the designer.
    InitializeComponent()

    TextBox1.Tag = "Default text"  ' This can be set with the designer
    TextBox1.Text = CStr(TextBox1.Tag)
End Sub

Private Sub OnTextBoxTextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles TextBox1.TextChanged
    Dim textbox As TextBox = DirectCast(sender, TextBox)

    If String.IsNullOrEmpty(textbox.Text) Then
        textbox.Text = CStr(textbox.Tag)
        textbox.SelectAll()
    End If
End Sub

Of course, you can also achieve similar behavior using native Windows functionality, but a few lines of managed code will give you pretty much all you need even if you do not want to use Win32.

default text handling in a text box

Private Sub Form2_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
    TextBox1.Text = "Default Text" ' initialize the text box 
End Sub

clear the text when the cursor is in the text box

Private Sub TextBox1_GotFocus(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles TextBox1_GotFocus
    TextBox1.Text = "" ' clear the text box for typing
End Sub

If the text box remains empty after data change then the default text comes again

Private Sub TextBox1_LostFocus(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles TextBox1_LostFocus
    TextBox1.Text = "" ' clear the text box for typing
End Sub

Are you looking for something like this?

If Textbox.Text = string.Empty Then
TextBox.Text = "Default Text"
End If

I would create a class that inherits TextBox and do two things with it:

• Add DefaultText string property
• Override the Text setter to always set this DefaultText if the new Text value is String.Empty

I assume you meant to add text from the aspx page.

<asp:TextBox ID="TextBox1" runat="server" value="Default Value"></asp:TextBox

Even when .NET don't suggest this feature in the intellitext, I assume that it will allow you to put any attribute, even custom that you can manipulate data in it. But, it does the work. and the value attribute is sent to the browser, therefore, initiate in the text field.

For TextArea (TextMode="MultiLine"), you can put between the tags.

<asp:TextBox ID="TextBox1" runat="server" TextMode="MultiLine">Text Here will be inside the TextArea</asp:TextBox>

It is like html textarea tag behave.