In my last post, I walked through a simple example of an ActionResult that you can use to transmit a file to the user’s browser along with a download prompt.
The MVC framework will include several useful action results for common tasks. However, we might not cover all results you might want to return. In this post, I walk through a simple result that will cover all remaining cases. With the DelegatingResult, you simply pass it a delegate. This provides ultimate control. Let’s see it in action.
public ActionResult Hello() {
return new DelegatingResult(context => {
context.HttpContext.Response.AddHeader("something", "something");
context.HttpContext.Response.Write("Hello World!");
});
}
Notice that we pass in a lambda to the constructor of the action result. This lambda is a delegate of type Action<ControllerContext>. By doing this, the lines of code within that block (Response.AddHeader and Response.Write) are deferred till later.
Here’s the code for this action result.
public class DelegatingResult : ActionResult {
public Action<ControllerContext> Command {
get;
private set;
}
public DelegatingResult(Action<ControllerContext> command) {
this.Command = command;
}
public override void ExecuteResult(ControllerContext context) {
if (context == null) {
throw new ArgumentNullException("context");
}
Command(context);
}
}
I updated the sample I wrote in my last post to include this demo. Download the source.