Question

Could you please suggest an elegant way to check if a data on the view has been modified to enable the Save button accordingly?

Thanks.

Answer 1

Assuming you are using MVVM with Caliburn.micro, there is a Can-convention for commands. So, assuming you want to enable Save button if a string property named Username is non-empty, you simply add this method to the viewmodel:

public bool CanSave()
{
    if(String.IsNullOrEmpty(UserName))
        return false;

    return true;
}

Assuming your class inherits PropertyChangedBase or Screen, and you have a button with Name=”Save”, it will be disabled if UserName is empty. If you are interested in data changing in the view, the relevant property, in this example UserName, would of course have to be bound to some input area in the view – you could for instance have a TextBox named UserName which would make Caliburn set up the binding by convention.

The class in its entirety would then look something like this:

Edited to only allow saving of actually different data

public class UserViewModel : PropertyChangedBase
{
    private string _savedUserName;

    public string UserName{ get; set; }

    public bool CanSave()
    {
        return !UserName.Equals(_savedUserName);
    }

    public void Save()
    {
        //Save the data

        _savedUserName = UserName;
    }
}