Change the borderColor of the TextBox

Question

How can I change the BorderColor of the Textbox when a user Clicks on it or focuses on it?

Answer 1

You can handle WM_NCPAINT message of TextBox and draw a border on the non-client area of control if the control has focus. You can use any color to draw border:

using System; using System.Drawing; using System.Runtime.InteropServices; using System.Windows.Forms; public class ExTextBox : TextBox {     [DllImport("user32")]     private static extern IntPtr GetWindowDC(IntPtr hwnd);     private const int WM_NCPAINT = 0x85;     protected override void WndProc(ref Message m)     {         base.WndProc(ref m);         if (m.Msg == WM_NCPAINT && this.Focused)         {             var dc = GetWindowDC(Handle);             using (Graphics g = Graphics.FromHdc(dc))             {                 g.DrawRectangle(Pens.Red, 0, 0, Width - 1, Height - 1);             }         }     } } 

Result

The painting of borders while the control is focused is completely flicker-free:

BorderColor property for TextBox

In the current post I just change the border color on focus. You can also add a BorderColor property to the control. Then you can change border-color based on your requirement at design-time or run-time. I've posted a more completed version of TextBox which has BorderColor property: in the following post:

• BorderColor property for TextBox

Answer 2

try this

bool focus = false; private void Form1_Paint(object sender, PaintEventArgs e) {     if (focus)     {         textBox1.BorderStyle = BorderStyle.None;         Pen p = new Pen(Color.Red);         Graphics g = e.Graphics;         int variance = 3;         g.DrawRectangle(p, new Rectangle(textBox1.Location.X - variance, textBox1.Location.Y - variance, textBox1.Width + variance, textBox1.Height +variance ));     }     else     {         textBox1.BorderStyle = BorderStyle.FixedSingle;     } }  private void textBox1_Enter(object sender, EventArgs e) {     focus = true;     this.Refresh(); }  private void textBox1_Leave(object sender, EventArgs e) {     focus = false;     this.Refresh(); }