Question

I’m trying to create a search tool and would like to display the results in a text box, much like the one contained in Visual Studio – this means that for long searches results will be appended to the end of the text box while the user is attempting to look at the results at the top of the text box.

At the moment I’m using a standard textbox, however it has many problems:

• The text box flickers madly while the search is in progress
• Its not possible for the user to scroll while results are being appended to the box
• Its not possible for the user to copy and paste results in the text box while results are being appended.

Are there any ways of working around these issues, or should I look into using another control / creating my own?

Answer 1

Microsoft forgot to implement the Begin/EndUpdate() methods for TextBox. You can add them yourself, it solves the problem. You can’t get rid of the flicker though. Sample code:

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

namespace WindowsFormsApplication1 {
    public partial class Form1 : Form {
        public Form1() {
            InitializeComponent();
            timer1.Interval = 10;
            timer1.Tick += new EventHandler(timer1_Tick);
            button1.Click += new EventHandler(button1_Click);
        }
        void timer1_Tick(object sender, EventArgs e) {
            int pos = textBox1.SelectionStart;
            int len = textBox1.SelectionLength;
            SendMessage(textBox1.Handle, 11, IntPtr.Zero, IntPtr.Zero);
            textBox1.AppendText(DateTime.Now.ToString() + Environment.NewLine);
            SendMessage(textBox1.Handle, 11, (IntPtr)1, IntPtr.Zero);
            //if (textBox1 is RichTextBox) textBox1.Invalidate();
            textBox1.SelectionStart = pos;
            textBox1.SelectionLength = len;
        }
        private void button1_Click(object sender, EventArgs e) {
            timer1.Enabled = !timer1.Enabled;
        }
        [DllImport("user32.dll")]
        private static extern IntPtr SendMessage(IntPtr hWnd, int msg, IntPtr wp, IntPtr lp);
    }
}