Textbox padding

As you have most likely discovered, Winforms Textboxes do not have a padding property. Since Panels do expose a Padding property, one technique would be to:

1. Create a Panel
2. Set its border to match a Textbox (e.g., Fixed3D)
3. Set its background color to match a Textbox (e.g., White or Window)
4. Set its padding to your satisfaction (e.g., 10,3,10,3)
5. Add a Textbox inside the panel
6. Set the Textbox's border to none
7. Play with the Textbox's Dock and Anchor properties do get desired effect

This should get you started. You could also create a custom control that does the same thing as mentioned above.

In case you were talking about Textboxes in asp.net, just use CSS:
input[type="text"] {padding: 3px 10px}

OK, here is a proper solution. First of all set Multiline of your TextBox control to true.

Needed using statements:

using System.Drawing;
using System.Runtime.InteropServices;
using System.Windows.Forms;

Code:

private const int EM_SETRECT = 0xB3;

[DllImport(@"User32.dll", EntryPoint = @"SendMessage", CharSet = CharSet.Auto)]
private static extern int SendMessageRefRect(IntPtr hWnd, uint msg, int wParam, ref RECT rect);

[StructLayout(LayoutKind.Sequential)]
private struct RECT
{
    public readonly int Left;
    public readonly int Top;
    public readonly int Right;
    public readonly int Bottom;

    private RECT(int left, int top, int right, int bottom)
    {
        Left = left;
        Top = top;
        Right = right;
        Bottom = bottom;
    }

    public RECT(Rectangle r) : this(r.Left, r.Top, r.Right, r.Bottom)
    {
    }
}
public void SetPadding(TextBox textBox, Padding padding)
{
    var rect = new Rectangle(padding.Left, padding.Top, textBox.ClientSize.Width - padding.Left - padding.Right, textBox.ClientSize.Height - padding.Top - padding.Bottom);
    RECT rc = new RECT(rect );
    SendMessageRefRect(textBox.Handle, EM_SETRECT, 0, ref rc);
}

Now call like so:

SetPadding(myTextBox, new Padding(5, 5, 5, 5));

Of course, best is to create your own TextBox control which can automatically set Multiline to true and stop unwanted lines breaks in the text etc..