wpf - Error message in a property -

this problem. if user type number in textbox right, if type char, don't see messagebox () in property. why ?

<textbox horizontalalignment="left"           tabindex="12"           text="{binding time_hh, updatesourcetrigger=propertychanged,stringformat='{}{##}'}"           flowdirection="righttoleft"            maxlength ="2"           height="30"           width="30" /> 

and property

private _time_hh integer  public property time_hh() integer             return _time_hh     end     set(value integer)         = 0 len(value.tostring)             if isnumeric(value.tostring(i)) = false                 messagebox.show("error")                 value = 0             end if         next          _time_hh = value         onpropertychanged("time_hh")     end set end property 

your time_hh property integer, there's no way it's gonna contain non-numeric character.

at most, happen binding fail due type mismatch (is textbox showing red outline?)

if wanna check if user enters non-numeric characters, have use type allows so: string.

try this:

private _time_hh integer public property time_hh() string             return _time_hh.tostring()     end     set(value string)         = 0 len(value)             if isnumeric(value.tostring(i)) = false                 messagebox.show("error")                 value = 0             end if         next          _time_hh = integer.parse(value)         onpropertychanged("time_hh")     end set end property 

if need use numeric value, use integer field. create second property of type integer exposes field, if want use binding or (remember raise onpropertychanged property too, then, on time_hh setter)

caution - code above raise exception if user types "00,01-2,0". isnumeric returns true characters in string, doesn't mean correct number.

in opinion, better this:

private _time_hh integer public property time_hh() string             return _time_hh.tostring()     end     set(value string)         dim int integer          if integer.tryparse(value, int) = false             messagebox.show("error")         end if          _time_hh = int         onpropertychanged("time_hh")     end set end property 

sorry if did mistakes, code in c# , vb pretty rusty :p