用户控件中的绑定

Question

let's say I've got this code (in Winforms):

public class SomeClass
{
    public string Name { get; set; }
}

public partial class SomeControl : UserControl
{
    private SomeClass inClass;

    public string MyName { get; set; }

    public SomeControl(SomeClass someClass)
    {
        InitializeComponent();

        this.inClass = someClass;

        SetupBinding();
    }

    private void SetupBinding()
    {
        this.DataBindings.Clear();
        this.DataBindings.Add("MyName", this.inClass, "Name");
    }
}

If I'll change the the value of SomeClass.Name outside the user control, the property MyName never changes. What am I doing wrong?

Thank you

Answer 1

SomeClass must impelement INotifyPropertyChanged or have event named NameChanged if you want bidirectional data binding. You can implement it yourself, but I highly recommend Fody.PropertyChanged project.

PS: I wrote some extension method to create binding more easier and refactoring friendly way. In your case it would look like this:

this.BindTo(inClass, c => c.MyName , m => m.Name);

The method itself:

public static class BindingExtensions
{
    public static Binding BindTo<TControl, TControlProperty, TModel, TModelProperty>(this TControl control, TModel model, Expression<Func<TControl, TControlProperty>> controlProperty, Expression<Func<TModel, TModelProperty>> modelProperty, string format = null)
        where TControl : Control
    {
        var controlPropertyName = ((MemberExpression)controlProperty.Body).Member.Name;
        var modelPropertyName = ((MemberExpression)modelProperty.Body).Member.Name;

        var formattingEnabled = !string.IsNullOrWhiteSpace(format);
        var binding = control.DataBindings.Add(controlPropertyName, model, modelPropertyName, formattingEnabled, DataSourceUpdateMode.OnPropertyChanged);
        if (formattingEnabled)
        {
            binding.FormatString = format;
        }
        return binding;
    }
}