Disable spacekey textbox in c# wpf -

i have textbox need allow numbers, delete , backsapce. code works this, allowing space key though disabled it. i'm not sure missing here.

public class numbertextbox : textbox {     /// <summary>     /// allows numbers, delete, backspace keys     /// </summary>     public numbertextbox()     {         keydown += new keyeventhandler(onkeydown);     }      private bool isnumberkey(key inkey)     {         if (inkey < key.d0 || inkey > key.d9)         {             if (inkey < key.numpad0 || inkey > key.numpad9)             {                 return false;             }         }         return true;     }      private bool isactionkey(key inkey)     {         return inkey == key.delete || inkey == key.back;     }      private bool isspacekey(key inkey)     {         if (inkey == key.space)         {             return true;         }         return false;     }      protected void onkeydown(object sender, keyeventargs e)     {         e.handled = !isnumberkey(e.key) && !isactionkey(e.key) && isspacekey(e.key);     }  } 

from microsoft website:

public class numerictextbox : textbox {     bool allowspace = false;      // restricts entry of characters digits (including hex), negative sign,     // decimal point, , editing keystrokes (backspace).     protected override void onkeypress(keypresseventargs e)     {         base.onkeypress(e);          numberformatinfo numberformatinfo = system.globalization.cultureinfo.currentculture.numberformat;         string decimalseparator = numberformatinfo.numberdecimalseparator;         string groupseparator = numberformatinfo.numbergroupseparator;         string negativesign = numberformatinfo.negativesign;          string keyinput = e.keychar.tostring();          if (char.isdigit(e.keychar))         {             // digits ok         }         else if (keyinput.equals(decimalseparator) || keyinput.equals(groupseparator) ||          keyinput.equals(negativesign))         {             // decimal separator ok         }         else if (e.keychar == '\b')         {             // backspace key ok         }         //    else if ((modifierkeys & (keys.control | keys.alt)) != 0)         //    {         //     // let edit control handle control , alt key combinations         //    }         else if (this.allowspace && e.keychar == ' ')         {          }         else         {             // swallow invalid key , beep             e.handled = true;             //    messagebeep();         }     }      public int intvalue     {                 {             return int32.parse(this.text);         }     }      public decimal decimalvalue     {                 {             return decimal.parse(this.text);         }     }      public bool allowspace     {         set         {             this.allowspace = value;         }                  {             return this.allowspace;         }     } }