c# - Bind command in WPF using MVVM

Question

I am learning MVVM and WPF. I have a xaml file in my project and which has a simple click event handler in the code behind.

Now I want to do the same in MVVM. I read a lot of articles and also read many answers in sof. But still unable to do this.

Can anyone please give a simple example in which a button click event is done in MVVM.

Edit

<Window x:Class="WhiteBalance.BaseCalWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:uc="clr-namespace:NumberUpDownControl;assembly=NumberUpDownControl"
        xmlns:viewn="clr-namespace:WhiteBalance.ViewModels"
        Title="RefImgSettingWindow"  Height="900" Width="1000" ResizeMode="NoResize" 
        BorderThickness="4">
    <Window.Resources>
        <viewn:DashBoardViewModel x:Key="demokey"></viewn:DashBoardViewModel>
    </Window.Resources>
    <Grid x:Name="gdParent" DataContext="{StaticResource demokey}">
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="490" />
            <ColumnDefinition Width="488*" />
        </Grid.ColumnDefinitions>
        <Grid.RowDefinitions>
            <RowDefinition Height="300" />
            <RowDefinition Height="300" />
            <RowDefinition Height="*" />
        </Grid.RowDefinitions>
        <StackPanel Grid.Row="0" Grid.Column="0">
            <Label Content="{Binding Path=NAME,Mode=TwoWay}" Height="28" Name="lblTest" />
            <Button Content="Capture" Height="23" Name="btnCapture" Width="75" Command="{Binding Path=SaveCommand}"
                             Canvas.Left="94" Canvas.Top="254" />

        </StackPanel>
    </Grid>
</Window>

namespace WhiteBalance.ViewModels
{
    public class DashBoardViewModel: ObservableObject
    {
        private string _name = "dsqdasd";

        public string NAME
        {
            get { return _name; }
            set { _name = value; }
        }

        public ICommand SaveCommand
        {
            get;
            set;
        }

        private bool CanExecuteSaveCommand()
        {
            return true;    // !string.IsNullOrEmpty(LastName);
        }

        private void CreateSaveCommand()
        {
            SaveCommand = new RelayCommand(SaveExecute, CanExecuteSaveCommand);
        }

        public void SaveExecute()
        {
            //Person.Save(_newPerson);
            NAME = "Changed Name";
        }

        public DashBoardViewModel()
        {
            //objModel.TestText = "This will change";
            NAME = "TestName";
        }
    }
}

Thanks in advance.

Answer 1

You can bind the Command property of the button to any property that returns ICommand. Prism implements a nice convenient command called DelegateCommand that is very easy to use (here is a knock-off of it):

public ICommand MyButtonClickCommand 
{
    get { return new DelegateCommand<object>(FuncToCall, FuncToEvaluate); }
}

private void FuncToCall(object context)
{
    //this is called when the button is clicked
}

private bool FuncToEvaluate(object context)
{
    //this is called to evaluate whether FuncToCall can be called
    //for example you can return true or false based on some validation logic
    return true;
}



<Button x:Name="myButton" Command="{Binding MyButtonClickCommand}" />

The CodeProject example How to use Commands in WPF has a very similar example with code that you can easily work through. The previous Stack Overflow question has an example using RoutedCommands that are statically bound to: How to bind Close command to a button, and How to bind WPF button to a command in ViewModelBase? has a slightly more advanced example.