Throwing an exception from a SqlDataSource

member4953 · April 27th, 2009, 01:41 PM

Imar,

My Default.aspx has a GridView connected to a SqlDataSource. All is well if I can connect to the data source, which is done as the page is loading. If I cannot, for whatever reason, how do I throw an exception and handle it gracefully?

I have looked at the members of the SqlDataSource class and did not see anything I could use in Page_Load, for example.

Thomas

Imar · April 28th, 2009, 04:26 PM

Hi Thomas,

Not sure what you're asking exactly. The controls do already throw exceptions themselves when the database cannot be reached.

Some of the events (like Inserted) have an e argument with an Exception argument that you can check (and optionally handle by setting e.ExceptionHandled to True). The control fills the that property if it encounters a non-fatal exception.

Hope this helps,

Imar

member4953 · April 29th, 2009, 10:38 AM

Imar,

My confusion comes from this. I have a SqlSource that runs as the page opens to display data from which the user can chose. It is set up to bind and get some data from a specific database. All of that is "buried" in the SqlSource control, i.e., in the configuration of the data source.

If I run the application when the database is not available there is no code in the "Code Behind" to handle the exception. What event code should I create to handle the exception? For example, the "Databinding" event says that it "Fires when the controls databinding expressions are about to be evaluated." So if the control cannot bind I do not get the exception, right?

Perhaps I am having a conceptual problem, but I cannot see how to know that the database was not reached and inform my user gracefully.

Thomas

Imar · April 29th, 2009, 03:25 PM

Ah, I see. You have a few ways to handle this.

1. Use Page_Error to locally handle errors. A quick example:

Code:

 
protected void Page_Error(object sender, EventArgs e)
{
  Response.Write("Ooops");
  Context.ClearError();
}

This is a simple example that writes out a message. It's important to call ClearError or you still see the error on the page.

2. Globally handle erorrs. For more info, take a look at Chapter 17.

Cheers,

Imar