WPF MVVM RelayCommand Action, canExecute, parameter - wpf

Question

I´m using MVVM, I have defined a Command in a button. I want to use in this Command a parameter, execute an action and proving if Canexecute.
I have this RelayCommand
class RelayCommand<T> : ICommand
{
private readonly Action<T> _execute;
private readonly Func<T, bool> _canExecute;
/// <summary>
/// Initializes a new instance of the RelayCommand class that
/// can always execute.
/// </summary>
/// <param name="execute">The execution logic.</param>
/// <exception cref="ArgumentNullException">If the execute argument is null.</exception>
public RelayCommand(Action<T> execute)
: this(execute, null)
{
}
/// <summary>
/// Initializes a new instance of the RelayCommand class.
/// </summary>
/// <param name="execute">The execution logic.</param>
/// <param name="canExecute">The execution status logic.</param>
/// <exception cref="ArgumentNullException">If the execute argument is null.</exception>
public RelayCommand(Action<T> execute, Func<T, bool> canExecute)
{
if (execute == null)
throw new ArgumentNullException("execute");
_execute = execute;
if (canExecute != null)
_canExecute = canExecute;
}
#region ICommand Members
public bool CanExecute(object parameter)
{
if (_canExecute == null)
return true;
if (parameter == null && typeof(T).IsValueType)
return _canExecute(default(T));
return _canExecute((T)parameter);
}
public event EventHandler CanExecuteChanged
{
add { CommandManager.RequerySuggested += value; }
remove { CommandManager.RequerySuggested -= value; }
}
public void Execute(object parameter)
{
_execute((T)parameter);
}
#endregion
}
With this button
<Button Grid.Row="4" Grid.Column="0" Grid.ColumnSpan="2"
Style="{StaticResource BotonSelect}" Width="200"
Command="{Binding ModificarLicenciaCommand}" >
<Label Content="Modificar Licencia" />
</Button>
And in the View Model.
ModificarLicenciaCommand = new RelayCommand(ModificarLicencia, CanModificarLicencia);
private bool CanModificarLicencia()
{
// Comprobar puedo modificar
return true;
}
private void ModificarLicencia()
{
// Modificar licencia
}
This is Ok, but I want to pass a parameter and using something like this:
CommandParameter="{Binding ElementName=DataGridLicencias}"
<Button Grid.Row="4" Grid.Column="0" Grid.ColumnSpan="2"
Style="{StaticResource BotonSelect}" Width="200"
Command="{Binding ModificarLicenciaCommand}"
CommandParameter="{Binding ., ElementName=DataGridLicencias}" >
<Label Content="Modificar Licencia" />
</Button>
and in viewModel:
RelayCommand< SfDataGrid >
ModificarLicenciaCommand = new RelayCommand<SfDataGrid>(ModificarLicencia, CanModificarLicencia);
private void ModificarLicencia(SfDataGrid dataGrid)
{
// Modificar licencia
}
Edit:
With this, I have an error in ModificarLicenciaCommand = new RelayCommand(ModificarLicencia, CanModificarLicencia)
In CanModificarLicentia ==> Error Argument2: cannot convert from 'method group' to 'Func'
Any help?

Answer 1

The following view model implementation should work:
public class ViewModel
{
public ViewModel()
{
ModificarLicenciaCommand = new RelayCommand<SfDataGrid>(ModificarLicencia, CanModificarLicencia);
}
private ICommand _modificarLicenciaCommand;
public ICommand ModificarLicenciaCommand
{
get { return _modificarLicenciaCommand; }
set { _modificarLicenciaCommand = value; }
}
private void ModificarLicencia(SfDataGrid dataGrid)
{
// Modificar licencia
}
private bool CanModificarLicencia(SfDataGrid dataGrid)
{
return true;
}
}

Answer 2

Example, you have a Button and a TextBox.
The button will only be Enable if the textbox's text is not empty:
In View:
<TextBox Name="txtCondition" Width="120" Height="35"/>
<Button Width="120" Height="35" Content="Click me!" Command="{Binding YourICommand}" CommandParameter="{Binding ElementName=txtCondition,Path=Text}">
In ViewModel:
public ICommand YourICommand { get; set; }
YourICommand = new RelayCommand<string>((str) =>
{
MessageBox.Show(str);
},(str) => { return !string.IsNullOrEmpty(str); });
Enjoy your code !