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Masked C# TextBox Control

, 21 Jan 2004
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A control that can be used for date, IP address, phone number, SSN, digit and decimal format input


The TextBox control is the most used control in a Windows program. It also cause a lot of problem either from QA or the user because of invalid data that was entered. Using a masked control will save a lot of time for the developer and reduce the complaints and bugs.

This masked intelligent user control enhances the function of the TextBox control, which can mask the Date, IP Address, SSN, Phone numbers, digits, decimal and checks the validation, and automatically set the delimiter location.

The property Masked is set to None by default and the control works like a normal TextBox control.
If setting the property to DateOnly, the control is masked to Date format.

It is intelligent.

What the user enters

What is Displayed

12 12/













Using the ErrorProvider to handle the invalidate input:

Creating Control:

  1. Start the Visual Studio.NET Windows Forms designer.
  2. Select a new C# project by clicking New from the File menu.
  3. Click Windows control library template on the templates.
  4. Set the Name MaskedTextBox

Then open the maskedTextBox.cs to Change the base class to the System.Windows.Forms.TextBox.

Adding a Property:

public enum Mask {None, DateOnly, PhoneWithArea, IpAddress, 
                  SSN, Decimal, Digit };
private Mask m_mask;
public Mask Maked
    get { return m_mask;}
    set {
        m_mask = value;

Override the OnKeyPress function

      this.KeyPress += new                                             

      private void OnKeyPress(object sender, KeyPressEventArgs e)
            MaskedTextBox sd = (MaskedTextBox) sender;           
            if (sd.m_IPAddrOnly)                                 
            if (sd.m_digitOnly)                                  
                  sd.MaskPhoneSSN(e, 3, 2);                      
                  sd.MaskPhoneSSN(e, 3, 3);                      

Unboxing the sender and using it to call these function is very important for multiple properties and when more than one control is used in one form, otherwise different controls may share the same variable with another control, which will cause unexpected results.

Double check the masked format:

private void OnLeave(object sender, EventArgs e)            
    MaskedTextBox sd = (MaskedTextBox) sender;            
    Regex regStr;                                         
        case Mask.DateOnly:                             
            regStr = new Regex(@"\d{2}/\d{2}/\d{4}"); 
                errorProvider1.SetError(this, "*"); 

        case Mask.PhoneWithArea:                        
            regStr = new Regex(@"\d{3}-\d{3}-\d{4}"); 

        case Mask.IpAddress:                            
            short cnt=0;                              
            int len = sd.Text.Length;                 
            for(short i=0; i<len;i++)                 
                if(sd.Text[i] == '.')               
                    if(i+1 < len)                 
                        if(sd.Text[i+1] == '.') 
                            errorProvider1.SetError(this, "*"); 
                    if(cnt < 3 || sd.Text[len-1] == '.')      
                        errorProvider1.SetError(this, "*"); 
        case Mask.SSN:                                  
            regStr = new Regex(@"\d{3}-\d{2}-\d{4}"); 
                errorProvider1.SetError(this, "*"); 
        case Mask.Decimal:                              

        case Mask.Digit:                                


After creating the DLL program, you should add the component into ToolBox. By:

  1. Right click the mouse in the ToolBox, and then select Customize Toolbox to open a dialog.
  2. Select the tab .Net framework component,
  3. Use the browser to find your DLL, check it, then click Ok.

The control should be in the ToolBox and it is ready to use.

That is all. I hope you enjoy it.


Update at 03/04/2002.
Using enum to set the properties.
Add Onleave function to check the invalidation of the controls.
Add Leap year check for Date mask in the CheckDayOfMonth funcrion.

12 July 2002 - updated source download

9 Nov 2003 - updated source download

If you have any comments or find some bugs, I would love to hear about it and make it better. You can reach me at Jibin Pan.


This article has no explicit license attached to it but may contain usage terms in the article text or the download files themselves. If in doubt please contact the author via the discussion board below.

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About the Author

Jibin Pan

United States United States
No Biography provided

Comments and Discussions

Questionabout new features Pinmemberglovkesh11-Sep-14 23:06 
Questioncan someone help me Pinmemberbabarkhalid24-Jun-14 22:52 
Questionversion mask PinmemberChris Anders28-May-14 21:18 
GeneralMy vote of 4 PinmemberFeb1925-Feb-13 23:08 
Generalshamsi date(yyyy/mm/dd) [modified] Pinmemberss_hellhound12-Nov-07 4:43 
QuestionCrystal Report for particullar where condition Pinmemberbagurtheen15-Feb-07 2:56 
GeneralMask for Email address PinmemberASysSolvers11-Dec-06 1:23 
GeneralRe: Mask for Email address PinmemberExpert Coming16-Jun-07 14:01 
GeneralHuge Bug Pinmembersubhash_c14-Apr-06 15:53 
QuestionHow to use with simple regular expression? PinmemberPerry211-Apr-06 13:52 
GeneralCopy/paste problem Pinsussjfloviou20-Jul-05 8:43 
Generalip problem Pinmemberranjithlogics11-May-05 20:04 
GeneralMaskedTextBox in SharpDevelop Pinmemberfuese27-Apr-05 5:27 
GeneralMask Ip... PinmemberRothariger18-Feb-05 8:31 
GeneralRe: Mask Ip... [modified] PinmemberPandaPKH14-Jun-06 1:09 
GeneralError Provider help Pinmemberbetterc11-Jul-04 4:27 
GeneralRe: Error Provider help Pinmemberbetterc15-Aug-04 10:22 
GeneralRe: Error Provider help PinmemberRogerDodge6-Nov-05 2:02 
GeneralRe: Error Provider help PinmemberSmartGuest17-Jan-11 5:32 
GeneralGerman date Pinmembersventek7-Jun-04 21:06 
GeneralRe: German date Pinmemberhaezeban17-Jun-04 11:37 
GeneralRe: German date Pinmemberhaezeban17-Jun-04 12:07 
GeneralRe: German date PinsussAnonymous16-Mar-05 12:48 
GeneralA simple example for regular expression Pinmemberjian-ping18-Dec-03 15:30 
Generaldate mask bug PinmemberEmanuele Zambrano15-Dec-03 9:16 

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