Binding Button click to a method

Question

I have a datagrid bound to an observable collection of objects   What I want to do is have a button that will execute a method of the object representing the row of the button that was clicked   So what I have now is something like this                lt DataGridTemplateColumn Header  Command  gt                   lt DataGridTemplateColumn CellTemplate gt                       lt DataTemplate gt                           lt Button Name  cmdCommand  Click   Binding Command                                    Content  Command   gt                       lt  DataTemplate gt                   lt  DataGridTemplateColumn CellTemplate gt               lt  DataGridTemplateColumn gt    Which doesn t work and reports the following error   Click   Binding Command   is not valid    Binding Command   is not a valid event handler method name  Only instance methods on the generated or code-behind class are valid   I ve looked at command binding but that looks like it would just end up going to a single external command instead of to the object bound to the row   I have it working using an event handler on the code behind and then routing it to the item bound to the selected row  since the row gets selected when the button is clicked  but that seems like poor way of handing this and I assume I m just missing something here

User · Answer

Some more explanations to the solution Rachel already gave    WPF Apps With The Model-View-ViewModel Design Pattern   by Josh Smith  http   msdn microsoft com en-us magazine dd419663 aspx

User · Answer

I do this all the time  Here s a look at an example and how you would implement it   Change your XAML to use the Command property of the button instead of the Click event  I am using the name SaveCommand since it is easier to follow then something named Command    lt Button Command   Binding Path SaveCommand     gt    Your CustomClass that the Button is bound to now needs to have a property called SaveCommand of type ICommand  It needs to point to the method on the CustomClass that you want to run when the command is executed   public MyCustomClass       private ICommand  saveCommand       public ICommand SaveCommand               get                       if   saveCommand    null                                 saveCommand   new RelayCommand                      param   gt  this SaveObject                         param   gt  this CanSave                                                return  saveCommand                       private bool CanSave                    Verify command can be executed here            private void SaveObject                    Save command execution logic           The above code uses a RelayCommand which accepts two parameters  the method to execute  and a true false value of if the command can execute or not  The RelayCommand class is a separate  cs file with the code shown below  I got it from Josh Smith          lt summary gt      A command whose sole purpose is to      relay its functionality to other     objects by invoking delegates  The     default return value for the CanExecute     method is  true        lt  summary gt  public class RelayCommand   ICommand        region Fields      readonly Action lt object gt   execute      readonly Predicate lt object gt   canExecute                endregion    Fields       region Constructors           lt summary gt          Creates a new command that can always execute           lt  summary gt           lt param name  execute  gt The execution logic  lt  param gt      public RelayCommand Action lt object gt  execute            this execute  null                        lt summary gt          Creates a new command           lt  summary gt           lt param name  execute  gt The execution logic  lt  param gt           lt param name  canExecute  gt The execution status logic  lt  param gt      public RelayCommand Action lt object gt  execute  Predicate lt object gt  canExecute                if  execute    null              throw new ArgumentNullException  execute              execute   execute           canExecute   canExecute                         endregion    Constructors       region ICommand Members       DebuggerStepThrough      public bool CanExecute object parameters                return  canExecute    null   true    canExecute parameters              public event EventHandler CanExecuteChanged               add   CommandManager RequerySuggested    value            remove   CommandManager RequerySuggested -  value               public void Execute object parameters                 execute parameters               endregion    ICommand Members

User · Answer

Click is an event   In your code behind  you need to have a corresponding event handler to whatever you have in the XAML   In this case  you would need to have the following   private void Command object sender  RoutedEventArgs e         Commands are different   If you need to wire up a command  you d use the Commmand property of the button and you would either use some pre-built Commands or wire up your own via the CommandManager class  I think

User · Answer

Here is the VB Net rendition of Rachel s answer above   Obviously the XAML binding is the same      lt Button Command   Binding Path SaveCommand     gt    Your Custom Class would look like this          lt summary gt      Retrieves an new or existing RelayCommand       lt  summary gt       lt returns gt  RelayCommand  lt  returns gt  Public ReadOnly Property SaveCommand   As ICommand     Get         If  saveCommand Is Nothing Then              saveCommand   New RelayCommand Function param  SaveObject    Function param  CanSave            End If         Return  saveCommand     End Get End Property Private  saveCommand As ICommand       lt summary gt      Returns Boolean flag indicating if command can be executed       lt  summary gt       lt returns gt  Boolean  lt  returns gt  Private Function CanSave   As Boolean       Verify command can be executed here      Return True End Function       lt summary gt      Code to be run when the command is executed       lt  summary gt       lt remarks gt Converted to a Function in VB net to avoid the  Expression does not produce a value  error  lt  remarks gt       lt returns gt  Nothing  lt  returns gt  Private Function SaveObject         Save command execution logic     Return Nothing End Function   And finally the RelayCommand class is as follows     Public Class RelayCommand   Implements ICommand  ReadOnly  execute As Action Of Object  ReadOnly  canExecute As Predicate Of Object  Private Event ICommand CanExecuteChanged As EventHandler Implements ICommand CanExecuteChanged       lt summary gt      Creates a new command that can always execute       lt  summary gt       lt param name  execute  gt The execution logic  lt  param gt  Public Sub New execute As Action Of Object       Me New execute  Nothing  End Sub       lt summary gt      Creates a new command       lt  summary gt       lt param name  execute  gt The execution logic  lt  param gt       lt param name  canExecute  gt The execution status logic  lt  param gt  Public Sub New execute As Action Of Object   canExecute As Predicate Of Object       If execute Is Nothing Then         Throw New ArgumentNullException  execute       End If      execute   execute      canExecute   canExecute End Sub   lt DebuggerStepThrough gt  Public Function CanExecute parameters As Object  As Boolean Implements ICommand CanExecute     Return If  canExecute Is Nothing  True   canExecute parameters   End Function  Public Custom Event CanExecuteChanged As EventHandler     AddHandler ByVal value As EventHandler          AddHandler CommandManager RequerySuggested  value     End AddHandler     RemoveHandler ByVal value As EventHandler          RemoveHandler CommandManager RequerySuggested  value     End RemoveHandler     RaiseEvent ByVal sender As Object  ByVal e As EventArgs          If   canExecute IsNot Nothing  Then              canExecute Invoke sender          End If     End RaiseEvent End Event  Public Sub Execute parameters As Object  Implements ICommand Execute      execute parameters  End Sub  End Class   Hope that helps any VB Net developers

User · Answer

You have various possibilies  The most simple and the most ugly is   XAML   lt Button Name  cmdCommand  Click  Button Clicked  Content  Command   gt     Code Behind  private void Button Clicked object sender  RoutedEventArgs e         FrameworkElement fe sender as FrameworkElement        YourClass fe DataContext  DoYourCommand                Another solution  better  is to provide a ICommand-property on your YourClass  This command will have already a reference to your YourClass-object and therefore can execute an action on this class   XAML   lt Button Name  cmdCommand  Command   Binding YourICommandReturningProperty   Content  Command   gt      Because during writing this answer  a lot of other answers were posted  I stop writing more  If you are interested in one of the ways I showed or if you think I have made a mistake  make a comment

[wpf] Binding Button click to a method

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