c# - Simple DataBinding in wpf application -

hi trying study simple data binding in wpf. tried , not succeeding.. please suggest ways..

<window x:class="wpftestapp.mainwindow"         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"         title="mainwindow" height="250" width="350">     <grid>         <grid.columndefinitions>             <columndefinition width="70"/>             <columndefinition width="*"/>         </grid.columndefinitions>         <grid.rowdefinitions>             <rowdefinition height="50"/>             <rowdefinition height="50"/>             <rowdefinition height="50"/>             <rowdefinition height="50"/>         </grid.rowdefinitions>          <label content="first name" grid.row="0" grid.column="0" height="25" horizontalalignment="stretch"/>         <label content="last name" grid.row="1" grid.column="0" height="25" horizontalalignment="stretch"/>         <label content="full name" grid.row="2" grid.column="0" height="25" horizontalalignment="stretch"/>          <textbox x:name="fname" text="{binding firstname, updatesourcetrigger=propertychanged}" grid.row="0" grid.column="1" height="25" horizontalalignment="stretch"/>         <textbox x:name="lname" text="{binding lastname, updatesourcetrigger=propertychanged}" grid.row="1" grid.column="1"  height="25" horizontalalignment="stretch"/>         <label x:name="lblfullname" content="{binding firstname}" grid.row="2" grid.column="1" height="25" horizontalalignment="stretch"/>         <button x:name="cmdcommand" content="command" grid.row="3" grid.column="1" margin="2" verticalalignment="center" horizontalalignment="center" click="cmdcommand_click"/>     </grid> </window> 

now see, want label lblfullname automatically updated type name in textboxes.

now codebehind file looks this:

  public partial class mainwindow : window, inotifypropertychanged     {         private string _firstname;         public string firstname         {             { return _firstname; }             set             {                 if (value != _firstname)                 {                     _firstname = value;                     onpropertychanged("firstname");                 }             }         }          private string _lastname;         public string lastname         {             { return _lastname; }             set             {                 if (value != _lastname)                 {                     _lastname = value;                     onpropertychanged("lastname");                 }             }         }          public event propertychangedeventhandler propertychanged;          /// <summary>         /// notifies objects registered receive event property value has changed.         /// </summary>         /// <param name="propertyname">the name of property changed.</param>         protected virtual void onpropertychanged(string propertyname)         {             if (this.propertychanged != null)             {                 this.propertychanged(this, new propertychangedeventargs(propertyname));             }         }          public mainwindow()         {             initializecomponent();         }          private void cmdcommand_click(object sender, routedeventargs e)         {             lblfullname.content = firstname + " " + lastname;         }      } 

needless say, clicking command button not working...

any suggestions?

setting datacontext point window solve immediate problem:

public mainwindow() {     initializecomponent();     this.datacontext = this; } 

the paths in binding expressions in xaml relative datacontext of controls datacontext has set.

however, suggest put first name , last name in separate class (e.g. personviewmodel) make code easier read , maintain.

public class personviewmodel : inotifypropertychanged {     private string _firstname;     public string firstname     {         { return _firstname; }         set         {             if (value != _firstname)             {                 _firstname = value;                 onpropertychanged("firstname");             }         }     }      private string _lastname;     public string lastname     {         { return _lastname; }         set         {             if (value != _lastname)             {                 _lastname = value;                 onpropertychanged("lastname");             }         }     }      public event propertychangedeventhandler propertychanged;      protected virtual void onpropertychanged(string propertyname)     {         var handler = this.propertychanged;         if (handler != null)         {             handler(this, new propertychangedeventargs(propertyname));         }     } }  public partial class mainwindow : window {     public mainwindow()     {         initializecomponent();         this.datacontext = new personviewmodel();     }      private void cmdcommand_click(object sender, routedeventargs e)     {         lblfullname.content = firstname + " " + lastname;     } } 

now last part of code not work anymore. there 2 solutions.

the quick , dirty solution:

    private void cmdcommand_click(object sender, routedeventargs e)     {          var person = this.datacontext personviewmodel;          if(person == null) return;          lblfullname.content = string.format("{0} {1}", person.firstname, person.lastname);     } 

a better way, when trying proper mvvm put property in viewmodel (note change in first , last name properties!):

public class personviewmodel : inotifypropertychanged {     public string fullname     {                  {             return string.format("{0} {1}", firstname, lastname);         }     }      private string _firstname;     public string firstname     {         { return _firstname; }         set         {             if (value != _firstname)             {                 _firstname = value;                 onpropertychanged("firstname");                 onpropertychanged("fullname");             }         }     }      private string _lastname;     public string lastname     {         { return _lastname; }         set         {             if (value != _lastname)             {                 _lastname = value;                 onpropertychanged("lastname");                 onpropertychanged("fullname");             }         }     }     // remainder of class remains same } 

remove button , click handler. bind label new property:

<label content="{binding fullname}"         grid.row="2" grid.column="1"         height="25" horizontalalignment="stretch"/>