multiline textbox auto adjust it's height according to the amount of text

Question

I have a textbox which can return various strings ranging from 5 characters upto 1000 characters in length. It has the following properties:

multiline = true
wordwrap = true

Which other properties of the textbox do I need to set to make the following possible?

The width of the box should be fixed
The height of the box to auto adjust depending on how much text it is returning e.g if the text runs onto 3 lines then it adjusts to 3 lines in height.

I don't see any `?` What is your question? Please don't write `how can I do that` — L.B, May 13 '12 at 20:40

Community Driven Business · Accepted Answer · 2012-05-13T21:41:47.117

10

Try this following code:

public partial class Form1 : Form
{
     private const int EM_GETLINECOUNT = 0xba;
     [DllImport("user32", EntryPoint = "SendMessageA", CharSet = CharSet.Ansi, SetLastError = true, ExactSpelling = true)]
     private static extern int SendMessage(int hwnd, int wMsg, int wParam, int lParam);


     public Form1()
     {
        InitializeComponent();
     }

     private void textBox1_TextChanged(object sender, EventArgs e)
     {
        var numberOfLines = SendMessage(textBox1.Handle.ToInt32(), EM_GETLINECOUNT, 0, 0);
        this.textBox1.Height = (textBox1.Font.Height + 2) * numberOfLines;
     }
}

edited May 13 '12 at 21:41

answered May 13 '12 at 21:06

Community Driven Business

4,622
1
16
20

If text box uses a custom font use `textBox1.Height = (textBox1.Font.Height + 2) * numberOfLines;` – George May 13 '12 at 21:24
1

...would I have been better using a different control than the textbox? do any of the controls have this functionality built into their properties? – whytheq May 14 '12 at 09:08
3

numberOflines = textbox1.lines.count(); – bh_earth0 Feb 04 '16 at 15:12

Harry Cutts · Answer 2 · 2012-05-13T21:03:53.077

There doesn't seem to be any functionality to do this built in to the TextBox class, but the Font class has a Height property that returns the number of pixels between baselines.

It is also possible to find out how many lines the text in the TextBox occupies, as described in this blog post (warning: it's not exactly elegant).

Once you've obtained this information, you should be able to make the TextChanged handler set the height of the TextBox accordingly using some simple maths.

score 3 · Answer 3 · edited May 23 '17 at 12:10

I can't believe there is still no really elegant way. This is what I puzzled out:

textBox.Height += textBox.GetPositionFromCharIndex(textBox.Text.Length - 1).Y 
    + 3 + textBox.Font.Height - textBox.ClientSize.Height;

This works by determining the pixel coordinates of the last character of the text.

You can execute this after setting the contents, i.e. in OnLoad of the Form or OnTextChanged of the TextBox control. If the fixed width changes when the user resizes the form, you should also take care of that, i.e. OnResize or OnClientSizeChanged.

TextBox supports the AutoSize property. However, it is already set to true by default, and it is not shown in the property editor or IntelliSense. It is just for font height changes and does not work when using MultiLine = true :( - this is not mentioned in the documentation.

Other options might include using a different control, like RichTextBox or Label. I didn't try yet, but it seems that a Label supports AutoSize much better.

score 2 · Answer 4 · answered Feb 21 '13 at 10:13

2

private void tb_TextChanged(object sender, EventArgs e)
{
    tb.Height = (tb.Text.Split('\n').Length + 2 ) * tb.Font.Height;
}

answered Feb 21 '13 at 10:13

vlad

61
4

now that the height is adjusting automatically the anchoring of to the form seem to be not working: the textbox is sometimes bigger than the form so I cannot see the bottom of the textbox. any ideas? – whytheq Jul 25 '15 at 18:58

George · Answer 5 · 2012-05-13T21:01:11.533

You need to adjust the height of the text box from code. Count the number of lines (this article here can help you with a way to do just that), then set the Textbox.Height to the value you need (number of line * 8px or so, depending on the font used inside the TextBox).

In the linked article solution was to override TextBox control class to be able to get the number of lines; there might be other ways to get the number of lines, but the suggested solution in the article looks quite elegant to me.

score 1 · Answer 6 · answered Oct 17 '19 at 07:00

1

Add MaxHeight property on TextBox as below.

<TextBox Name="txtSample" MaxHeight="1000" />

answered Oct 17 '19 at 07:00

Bharat Prasad Satyal

11
1

score 0 · Answer 7 · answered Nov 29 '13 at 08:10

Something like this gives the height of the text as how it is drawn in the textbox itself:

SizeF MessageSize = MyTextBoxControl.CreateGraphics()
                                .MeasureString(MyTextBoxControl.Text,
                                                MyTextBoxControl.Font,
                                                MyTextBoxControl.Width, 
                                                new StringFormat(0));

I am not sure what StringFormat should be but the values StringFormatFlags do not seem to apply to a default TextBox make up.

Now with MessageSize.Height you know the height of the text in the textbox.

multiline textbox auto adjust it's height according to the amount of text

7 Answers7

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