Raising Exceptions

In

<script runat="server" /> block or codebehind:

Private Sub Page_Load(Source As Object, E As EventArgs)

Dim _Connection As New

➥SqlConnection("Server=localhost;Database=pubs;uid=sa;pwd=;")

Dim _Command As New SqlCommand("Select * From Authors", _Connection)

Try

_Connection.Open()

DG1.DataSource = _Command.ExecuteReader(CommandBehavior.CloseConnection)

DG1.DataBind()

Catch _Error As Exception

Throw New Exception("Whoops.... You've got an error in the code!")

Finally

_Connection.Close()

End Try

End Sub

The Throw statement here creates a new exception and raises it, replacing the original

exception object.The error message that will appear on the page in this case is the one

that has been provided as an argument to the constructor of the Exception object.

The original error message can also be passed to the Throw statement in order to

show the details.You can achieve this by passing the Exception object as a second argument

to the constructor of the newly raised exception.

Catch _Error As Exception

Throw New Exception("Whoops.... You 've got an error in the code!", _Error)

Your exception message has been replaced by the original one, but your exception message

still appears.Where? Check out the Stack Trace section.

Comments

The Throw statement can be used to explicitly throw an exception or to rethrow a

caught exception.The new exception being raised is provided with a customized statement,

so as to hide error details and display a more simplified error message to the viewer.

You can also pass along the original exception object to the raised exception.This can

be useful because it allows a friendly error message to be displayed to the user, but keeps

the detailed information for debugging purposes.

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