Button not enabled even after providing CommandParameter in WPF

Question

I created a button whose commandparameter is set and command using a class that implements ICommand interface. But my button is disabled. Why is that? I got this code from here: ICommand is like a chocolate cake ``` ``` and my class is ``` class HelloWorldCommand:ICommand { public bool CanExecute(object parameter) { return parameter != null; } public event EventHandler CanExecuteChanged; public void Execute(object p…

Accepted Answer

Well, this is very-very simple implementation of `ICommand`.

As @JleruOHeP says, partially problem can be solved by swapping setters of `Command` and `CommandParameter`. But this is ugly way, because you have to remember the sequence every time.

More correct way is to tell `CommandManager` to re-query states of command:

```
public class HelloWorldCommand : ICommand
{
    public bool CanExecute(object parameter)
    {
        return parameter != null;
    }

public event EventHandler CanExecuteChanged
    {
        add { CommandManager.RequerySuggested += value; }
        remove { CommandManager.RequerySuggested -= value; }
    }

public void Execute(object parameter)
    {
        MessageBox.Show(parameter.ToString());
    }
}
```

Now the sequence of setters is indifferent. To understand how `CommandManager` works, you can read this nice article from Josh Smith.

Button not enabled even after providing CommandParameter in WPF

Solution

Problem