Question

I have 2 comboboxes in my xaml file. Basically when we double click the combobox in xaml file, it creates a combobox_selectionchanged event in xaml.cs file. I have done it as follows:

View Class:

<ComboBox Height="23" ItemsSource="{Binding BusRateList}" SelectedItem="{Binding SelectedBusRateItem}" SelectedIndex="2"  Name="comboBox2" SelectionChanged="comboBox2_SelectionChanged" />

<ComboBox Height="23" ItemsSource="{Binding BaudRateList}" SelectedItem="{Binding SelectedBaudRateItem}" SelectedIndex="6" Name="comboBox3" SelectionChanged="comboBox3_SelectionChanged" />

View.xaml.cs file:

private void comboBox2_SelectionChanged(object sender, SelectionChangedEventArgs e)
    {
        int id = Convert.ToInt32(comboBox2.SelectedIndex);            
        int speed = mI2c._busRate[id]; //mI2C is object of viewmodel class

        sendBuf[0] = Convert.ToByte((speed & 0xFF000000) >> 24);
        sendBuf[1] = Convert.ToByte((speed & 0x00FF0000) >> 16);
        sendBuf[2] = Convert.ToByte((speed & 0x0000FF00) >> 8);
        sendBuf[3] = Convert.ToByte(speed & 0x000000FF);

        cmd = (256 << 8 | 0x00);
        mCom.WriteInternalCommand(cmd, 4, ref sendBuf);

        ReadBusAndBaudRate();            
    }


private void comboBox3_SelectionChanged(object sender, SelectionChangedEventArgs e)
    {
        int id = Convert.ToInt32(comboBox3.SelectedIndex);            
        int speed = mI2c._baudRate[id]; //mI2C is object of viewmodel class
        sendBuf[0] = Convert.ToByte((speed & 0xFF000000) >> 24);
        sendBuf[1] = Convert.ToByte((speed & 0x00FF0000) >> 16);
        sendBuf[2] = Convert.ToByte((speed & 0x0000FF00) >> 8);
        sendBuf[3] = Convert.ToByte(speed & 0x000000FF);

        cmd = (256 << 8 | 0x00);
        mCom.WriteInternalCommand(cmd, 4, ref sendBuf);

        ReadBusAndBaudRate();
    }

public void ReadBusAndBaudRate()
    {          

        int speed = 100;

        // Some Code

        textBox1.Text = speed.ToString();

        textBox2.Text = speed.ToString();

        // Update message in Output Window as Effective Baud Rate
    }

ViewModel Class:

public ObservableCollection<int> _busRate;
public ObservableCollection<int> BusRateList
    {
        get { return _busRate; }
        set
        {
            _busRate = value;
            NotifyPropertyChanged("BusRateList");
        }
    }

    private int _selectedBusRate;
    public int SelectedBusRateItem
    {
        get { return _selectedBusRate; }
        set
        {
            _selectedBusRate = value;
            NotifyPropertyChanged("SelectedBusRateItem");
        }
    }      

    public ObservableCollection<int> _baudRate;
    public ObservableCollection<int> BaudRateList
    {
        get { return _baudRate; }
        set
        {
            _baudRate = value;
            NotifyPropertyChanged("BusRateList");
        }
    }

    private int _selectedBaudRate;
    public int SelectedBaudRateItem
    {
        get { return _selectedBaudRate; }
        set
        {
            _selectedBaudRate = value;
            NotifyPropertyChanged("SelectedBaudRateItem");
        }
    }

I have added around 8 items in both comboboxes in viewmodel constructor.

Now Using the above properties I want to perform the combobox selection changed event in viewmodel class which should execute all the statements which were done in my .cs file.

Please help!!!

Answer 1

Update viewmodel with ReadBusAndBaudRate() method and call this method in set of SelectedItem properties

public int SelectedBusRateItem
    {
        get { return _selectedBusRate; }
        set
        {
            _selectedBusRate = value;
             ReadBusAndBaudRate();
            NotifyPropertyChanged("SelectedBusRateItem");
        }
    }
    private int _selectedBaudRate;
    public int SelectedBaudRateItem
    {
        get { return _selectedBaudRate; }
        set
        {
            _selectedBaudRate = value;
            ReadBusAndBaudRate();
            NotifyPropertyChanged("SelectedBaudRateItem");
        }
    }

    private int _speed;
    public int Speed
    {
        get { return _speed; }
        set
        {
            _speed = value;
            NotifyPropertyChanged("Speed");
        }
    }


    private void ReadBusAndBaudRate()
    {
        //Do some code
        Speed = 10; // will be your logical value.
        //For message notifications use MVVM frameworks such as cinch by Sacha Barber
    }

• Update xaml with Binding Mode and TextBox binding for speed

• Add method fo mcom stuff as

    public int SelectedBaudRateItem
      {
          get { return _selectedBaudRate; }
          set
          {
              _selectedBaudRate = value;                   
              WriteMcomCommand(_selectedBaudRate );
              ReadBusAndBaudRate();
              NotifyPropertyChanged("SelectedBaudRateItem");
          }
      }    
      private void WriteMcomCommand(int id)
      {
      int speed = mI2c._busRate[id]; //mI2C is object of viewmodel class
  
      sendBuf[0] = Convert.ToByte((speed & 0xFF000000) >> 24);
      sendBuf[1] = Convert.ToByte((speed & 0x00FF0000) >> 16);
      sendBuf[2] = Convert.ToByte((speed & 0x0000FF00) >> 8);
      sendBuf[3] = Convert.ToByte(speed & 0x000000FF);
  
      cmd = (256 << 8 | 0x00);
      mCom.WriteInternalCommand(cmd, 4, ref sendBuf);
      }