CODEWITHSUNDEEP
wpfmvvm
CoderForHire
CoderForHire

Reputation: 455

WPF MVVM Determine When Item in Collection On Model Changes

I have a DataGrid bound to a list of Job Models. The Job Model has a JobName property.

I can tell when a row is selected because the grid's SelectedItem is set, But when the user changes some data in the grid, I'd like to do some things in the view model.

When the user changes the JobName on the active row in the grid, how can the View Model know about it?

Upvotes: 1

Views: 2110

Answers (3)

jimSampica
jimSampica

Reputation: 12420

Have your model implement INotifyPropertyChanged. Then when you fill the Job list from your DAL register your model items with your propertyChanged event handler

View Model Class:

public class JobsViewModel
{
    public List<Job> Jobs { get; set; }

    public JobsViewModel()
    {
        //Get your list of items and add your handler method for each item that is added
        Jobs = new List<Job>();
        Job job = new Job("Joe");
        job.PropertyChanged += job_PropertyChanged;
        Jobs.Add(job);

    }

    private void job_PropertyChanged(object sender, PropertyChangedEventArgs e)
    {
        //Do stuff with job here
    }
}

Job Class:

public class Job : INotifyPropertyChanged
{
    private string _jobName;
    public string JobName 
    {
        get { return _jobName; }
        set
        {
            _jobName = value;
            OnPropertyChanged("JobName");
        }
    }

    public Job(string jobName)
    {
        JobName = jobName;
    }

    public event PropertyChangedEventHandler PropertyChanged;

    protected void OnPropertyChanged(string name)
    {
        PropertyChangedEventHandler handler = PropertyChanged;
        if (handler != null)
        {
            handler(this, new PropertyChangedEventArgs(name));
        }
    }
}

Upvotes: 1

Natxo
Natxo

Reputation: 2947

Your JobName property should something like:

public string JobName
{
    get { return _jobName; }
    set
    {
        _jobName = value;
        this.OnPropertyChanged("JobName");
    }
}

When user changes it the datagrid, the setter will be called and you can add some logic there. Binding should be TwoWay (as is by default) for this to work.

If you need to listen to property changes in your viewmodel, an easy way is to add this in the constructor:

jobModel.PropertyChanged += new System.ComponentModel.PropertyChangedEventHandler(JobModel_PropertyChanged);

Then in the JobModel_PropertyChanged method you can check which property has changed and react.

Upvotes: 1

Chevul Ervin
Chevul Ervin

Reputation: 883

If there is a two way binding the JobName property setter of your JobModel instance will be invoked. If the setter raises the PropertyChanged event you can handle that event in the ViewModel by registering and unregistering the handler when the selected item changes.

Upvotes: 1

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