How to pass parameters to command using multibinding?

Question

I am using MVVM tool kit version1. I have two Text boxes textbox1 and textbox2. I need to pass these two values as parameter when pressing on button and need to show the result on a third Text Box named textbox3.

my VM code similar like this

public ICommand AddCommand
    {
        get
        {
            if (addCommand == null)
            {
                addCommand = new DelegateCommand<object>(CommandExecute,CanCommandExecute);
            }
            return addCommand;
        }
    }

    private void  CommandExecute(object parameter)
    {
        var values = (object[])parameter;
        var a= (int)values[0];
        var b= (int)values[1];
        Calculater calcu = new Calcu();
        int c = calcu.sum(a, b);      
    }

    private bool  CanCommandExecute(object parameter)
    {
        return true;  
    }

The commandExecute method is called when the user click on the button but my the parameter argument doesn't not have any value. how i can pass the user's values as parameter?. and return the result to the texbox3?

Answer 1

you can use Multibinding and a Converter

<Button Content="Add" Command="{Binding AddCommand}"
 <Button.CommandParameter>
    <MultiBinding Converter="{StaticResource YourConverter}">
         <Binding Path="Text" ElementName="txt1"/>
         <Binding Path="Text" ElementName="txt2"/>
    </MultiBinding>
 </Button.CommandParameter>
</Button>

converter

public class YourConverter : IMultiValueConverter
{
 public object Convert(object[] values, ...)
 {
    //.Net4.0
    return new Tuple<int, int>((int)values[0], (int)values[1]);

    //.Net < 4.0
    //return values.ToArray();
 }

 ...
}

command

private void  CommandExecute(object parameter)
{
    var o= (Tuple<int, int>)parameter;
    var a= o.Item1;
    var b= o.Item2;
    Calculater calcu = new Calcu();
    int c = calcu.sum(a, b);      
}

ps: pls check my syntax - its written from my mind...

Answer 2

You can make Properties in your ViewModel and bind it to your TextBoxs you need to use INotifyPropertyChanged to Notify the change....

View Model

public MyViewModel:INotifyPropertyChanged
{
private string1;
private string2;
private string3;

//Make a similar propety for string2 and string3
public string String1
{         
    get         
    {            
        return string1;         
    }
    set
    {
        string1=value;
        //Implementation of Propertychanged is left upon you
        InvokePropertyChanged("String1");
    }     
}    


public ICommand AddCommand     
{         
    get         
    {             
        if (addCommand == null)             
        {                 
            addCommand = new DelegateCommand<object>(CommandExecute,CanCommandExecute);             
        }             
        return addCommand;         
    }     
}      
private void  CommandExecute(object parameter)     
{           
    var a= String1;         
    var b= String2;         
    Calculater calcu = new Calcu();         
    String3 = (calcu.sum(a, b)).ToString();           
}      
private bool  CanCommandExecute(object parameter)     
{         
    return true;       
}
}

Xaml

<TextBox Text={Binding Path=String1}></TextBox>
<TextBoxText={Binding Path=String2}></TextBox>
<Button Command={Binding Path=AddCommand}>Add</Button>
<TextBoxText={Binding Path=String3></TextBox>