How to create custom TextBox control?

Question

I want to perform Trim() method on each TexBox control on my page, before value is returned. I dont' want to hard-code the same code for each TexBox control, I want to do it in more elegant way.

I've found made the following class

namespace System.Web.UI.WebControls
{
    public partial class TrimmedTextBuox : TextBox
    {
        private string text;
        public override string Text
        {
            get { return string.IsNullOrEmpty(text) ? text : text.Trim(); }
            set { text = value; }
        }     
    }
}

but it fails, while debuggind the compiler doesn't get inside get{} and set{}.

After that, I created a UserControl item, but it must be deriverd from System.Web.UI.UserControl, not System.Web.UI.WebControls.TextBox to get it work (there's an exception which points to that)

So, how can I do that ?

How are you calling your `TrimmedTextBuox` ? I'm afraid that your not using the custom control that you've created! — Thiago Vinicius, Jan 23 '14 at 11:17
Try this `public new string Text` instead of `public override string Text` — alfoks, Jan 23 '14 at 11:17
IMO 'set' should be trimmed like text = value.Trim() not 'get'. — anuragal, Jan 23 '14 at 11:19
It seems correct. Check Thiago Vinicius comment. Do you have a `TrimmedTextBuox tbox = new TrimmedTextBuox();` somewhere in your code? — alfoks, Jan 23 '14 at 11:23
hmm, I thought that partial class should fit for standard control — Tony, Jan 23 '14 at 11:31
@Tony `partial` is used when you want to define the class in more than one plcaes (2 files for example). You need to use the class you created, not `TextBox` — alfoks, Jan 23 '14 at 11:51

score 3 · Answer 1 · answered Jan 23 '14 at 12:29

First you have to register your control in your .aspx page like that:

<%@ Register TagPrefix="customControls" Namespace="WebApplication.Custom.Controls" Assembly="WebApplication"%>

Then you can call it using the markup

<customControls:TrimmedTextBuox  ID="txtTrim" runat="server"/>

Plus you don't have to create another "text" property in your custom TextBox. Instead, it can be done like that:

namespace WebApplication.Custom.Controls
{
    public class TrimmedTextBuox : TextBox
    {
        public override string Text
        {
            get
            {                
                return base.Text;
            }
            set
            {
                if (!String.IsNullOrEmpty(value))
                    base.Text = value.Trim();
            }
        }
    }
}

score 0 · Answer 2 · answered Jan 23 '14 at 11:14

This will trim recursively all text boxes before inserting.

 public static void trimRecursive(Control root)
    {
      foreach (Control control in root.Controls)
      {
        if (control is TextBox)
        {
            var textbox = control as TextBox;
            textbox.Text = textbox.Text.Trim();
        }
        else
        {
            trimRecursive(control);
        }
    }
}

protected void Button1_Click(object sender, EventArgs e)
{
    trimRecursive(Page);
}

score 0 · Answer 3 · edited May 23 '17 at 11:56

Simple Solution to your problem is to hide the Text property of your base class by using new keyword. sample code...

public class TrimmedTextBox : TextBox
{
    public new string Text
    {
        get
        {
             var t = (string) GetValue(TextProperty);
            return t != null ? t.Trim() : string.Empty;
        }
    }
}

For more info about how new keyword with property works refrer to this SO Question

How to create custom TextBox control?

3 Answers3