MultiBinding

MultiBinding class represents a collection of Binding objects bound to a single target property. So it's quite similar to the WPF MultiBinding but for Windows Forms.

Also it's a descendant of Binding class so it has all the same members but with the following differences:

• Constructor of MultiBinding does not allow to specify data source and data member. Binding value retrieved from nested bindings as an array of values.
• Nested bindings should be added/removed using special methods:
  • AddBinding method creates and returns a nested binding. Signature of the method is similar to signature of Binding constructor but without a name of target property.
  • RemoveBinding method removes nested binding created with the AddBinding method.
• Unfortunately multi-bindings can not be just added to DataBindings collection of controls, AddTo and RemoveFrom methods should be used for that.

Example

For example, MultiBinding can be used to enable button only if both text-boxes are not empty:

// Create instance of one-way MultiBinding with "Enabled" target property
var multiBinding = new MultiBinding(nameof(Button.Enabled), dataSourceUpdateMode: DataSourceUpdateMode.Never);

// Add two nested bindings with text-boxes as data-sources and "Text" property as a data-member
multiBinding.AddBinding(textBoxA, nameof(TextBox.Text));
multiBinding.AddBinding(textBoxB, nameof(TextBox.Text));

// Convert array of values of nested bindings to a target value
multiBinding.Format += (sender, args) => args.Value = ((Object[]) args.Value).Cast<String>().All(value => !String.IsNullOrEmpty(value));

// Add multi-binding to the button
multiBinding.AddTo(button.DataBindings);

More examples can be found in the demo-project.