Question

I have large switch statement in which I create UIElements based on input value from XElement:

public static UIElement CreateElement(XElement element) {
            var name = element.Attribute("Name").Value;
            var text = element.Attribute("Value").Value;
            var width = Convert.ToDouble(element.Attribute("Width").Value);
            var height = Convert.ToDouble(element.Attribute("Height").Value);
            //...
            switch (element.Attribute("Type").Value) {
                case "System.Windows.Forms.Label":
                    return new System.Windows.Controls.Label() {
                        Name = name,
                        Content = text,
                        Width = width,
                        Height = height
                    };
                case "System.Windows.Forms.Button":
                    return new System.Windows.Controls.Button() {
                        Name = name,
                        Content = text,
                        Width = width,
                        Height = height
                    };
                    //...
                default:
                    return null;
            }
        }

I am creating a lot controls like this and as you can see, too much repetition is going on.

Is there some way to avoid this repetition? Thanks in advance for ideas.

Answer 1

You could create a generic function that does the create:

private static Create<T>(string name, string text, double width, double height) where T: Control, new()
{
   return new T { Name = name, Content = text, Width = width, Height = height }
}

Your switch then becomes:

switch (element.Attribute("Type").Value) {
  case "System.Windows.Forms.Label" : return Create<System.Windows.Forms.Label>(name, text, width, height);
  etc.
}

You could also adapt this to pass in the XElement, whichever you prefer.

If the Type attribute is always the name of the System.Type you want, then you could just do

Control ctrl = (Control) Activator.CreateInstance(Type.GetType(element.Attribute("Type").Value));
ctrl.Name = name;
etc.

If there’s a one to one mapping between the value of the attribute and the type you want, then you can declare a readonly static field with the mapping:

private static readonly uiTypeMapping = new Dictionary<string,Type> {
  { "System.Windows.Forms.Label", typeof(System.Windows.Controls.Label) },
  { "System.Windows.Forms.Button", typeof(System.Windows.Controls.Button) },
  { etc. }
};

And use

UIElement elem = (UIElement) Activator.CreateInstance(uiTypeMapping[element.Attribute("Type").Value]);
etc.