Question

1)I have the PageBase class that inherits from Page Class. The all code behind inherit from PageBase class. So I want to add the exception handling logic to PageBase class.

In Page_Error Event I added the logic to handle the exception, but the I want page to be rendered properly with exception details showing on the top of Web Page.

e.g

On web form I have button control that updates the data in Database. On button click i have the logic to update the data. While updating it may throw exception. I dont want to put Try catch block on button click save logic. Instead I want some method or event on PageBase to catch the exception and render the page entirely with all controls and exception in the header.

2)`// in the Base class of CodeBehind page, I have Written

protected void TryAction(Action action)
{
  try
  {
    action();
  }
  catch(Exception e)
  {
    // write exception to output (Response.Write(str))
  }
}

In CodeBehind I have written the code for Button Click Event

Private List<T> GetData(string a, string b)
{
  List<T> _lst;
  TryAction(()=>{
     //Call BLL Method to retrieve the list of BO.
     _lst = BLLInstance.GetAllList(a,b);
  });
  return _lst;
}

This Works fine, I want,

Private List<T> GetData(string a, string b)
{
  TryAction(()=>{
     //Call BLL Method to retrieve the list of BO.
     return BLLInstance.GetAllList(a,b);
  });
}

It is Showing the Error”System.Action retuens void”, Can you please tell me how to use TryAction Method if we have return type.

Answer 1

When the exception is thrown, if you don’t catch it, it will bubble up to Page_Error and then Application_Error. Once it gets to Page_Error tho it’s already broken the page rendering. I don’t think there’s a way to continue rendering the rest of the page. If you’re looking to increase code re-use of your error handling logic you could use an anonymous method.

// on your base page
protected void TryAction(Action action)
{
    try
    {
        action();
    }
    catch(Exception e)
    {
        // write exception to output (Response.Write(str))
    }
}

protected void TryFunction<T>(Function<T> func)
{
    try
    {
        return func();
    }
    catch(Exception e)
    {
        // write exception to output (Response.Write(str))

        return default(T);// have to return something now because it's a function.
    }
}

then your data access method could look like

protected void Button1_Click(object sender, EventArgs e)
{
    TryAction(() => {
        // Do stuff here - save to database etc
    });
}

protected void Button1_Click(object sender, EventArgs e)
{
    return TryFunction<string>(() => {
        // Do stuff here - save to database etc
        return "woo";
    });
}

It is worth noting that if an exception occurs in the function you might not get a useful value back from it and you should code accordingly.