The textbox box under winform control cannot contain letters [Z]

Method 1:  Private   Void Tbox_keypress ( Object  Sender, keypresseventargs e ){  If (E. keychar = 0x20 ) E. keychar = ( Char ) 0 ; //  Disable Space key              If (E. keychar = 0x2d ) & (Textbox) sender). Text. Length =0 )) Return ; //  Process negative numbers              If (E. keychar> 0x20  ){  Try  {  Double . Parse (textbox) sender). Text + E. keychar. tostring ());}  Catch  {E. keychar = (Char ) 0 ; //  Handle invalid characters  }}} Method 2:  Private   Void Textbox_keypress ( Object  Sender, keypresseventargs e ){  If (E. keychar! = 8 &&! Char. isdigit (E. keychar) {e. Handled = True ;} Or  Private   Void Textbox_keypress ( Object  Sender, keypresseventargs e ){  If (E. keychar! = '  \ B  ' &&! Char. isdigit (E. keychar) {e. Handled = True  ;} Method 3:  Private   Void Textbox1_keypress (Object  Sender, system. Windows. Forms. keypresseventargs e ){  If (E. keychar! = '  \ B  ' ) //  This is the allowed backspace key  {  If (E. keychar < '  0  ' ) | (E. keychar> '  9 ' )) //  This is a 0-9 number.  {E. Handled = True  ; }}} Method 4:  Private   Void Textbox1_validating ( Object  Sender, canceleventargs e ){  Const   String Pattern = @"  ^ \ D + \.? \ D + $  " ;  String Content = (Textbox) sender). text;  If (! (RegEx. ismatch (content, pattern) {errorprovider1.seterror (Control) sender,  "  Only numbers are allowed!  "  ); E. Cancel = True  ;}  Else  Errorprovider1.seterror (Control) sender,  Null );} Method 5:  Private   Void Textbox1_keypress ( Object  Sender, system. Windows. Forms. keypresseventargs e ){  If (E. keychar = '  .  ' && This . Textbox1.text. indexof ( "  .  " )! =- 1 ) {E. Handled = True  ;}  If (! (E. keychar> = 48 & Amp; E. keychar <= 57 ) | E. keychar = '  .  ' | E. keychar = 8  ) {E. Handled = True  ;} Method 6:  Private   Void Tbx_lsregcapital_keypress ( Object  Sender, keypresseventargs e ){  If (! Char. isnumber (E. keychar )&&! Char. ispunctuation (E. keychar )&&! Char. iscontrol (E. keychar) {e. Handled = True ; //  Remove inappropriate characters  }  Else   If  (Char. ispunctuation (E. keychar )){ If (E. keychar! = '  .  ' | This . Textbox1.text. Length = 0 ) //  Decimal point  {E. Handled = True  ;}  If (Textbox1.text. lastindexof ( '  . ' )! =- 1  ) {E. Handled = True  ; }}} Method 7: ASCII code solution ,{  If (E. keychar <= 48 | E. keychar> = 57 ) & (E. keychar! = 8 ) & (E. keychar! = 46  ) E. Handled = True ; ====================== 48 represents 0, 57 represents 9, 8 represents space, 46 represents the decimal point}