How do I show Error Message using Managed Custom Actions with Windows Installer - error-handling

Question

I am writing a managed custom action. I am using the DTF Framework from Windows Installer Xml to wrap the managed dll into a usable CA dll. The CA does what it is supposed to, but I am still having trouble with error handling:
Dim record As New Record(1)
' Field 0 intentionally left blank
' Field 1 contains error number
record(1) = 27533
session.Message(InstallMessage.Error, record)
The above code produces the following text shown in the MSI log:
MSI (c) (C4 ! C6) [13:15:08:749]: Product: TestMSI -- Error 27533. The case-sensitive passwords do not match.
The error number refers to the code contained in the Error table within the MSI. The Message shown above is correct.
My problem is: Why does Windows Installer NOT create a dialog notifying the user about the error?

Answer 1

MSI can do this, but you need to OR in some extra values for the messageType argument.
eg.
Record record = new Record();
record.FormatString = string.Format("Something has gone wrong!");
session.Message(
InstallMessage.Error | (InstallMessage) ( MessageBoxIcon.Error ) |
(InstallMessage) MessageBoxButtons.OK,
record );
See this thread from the wix-users mailing list for more details.

Answer 2

I have run into the same problem, according to Wix: A Developer's Guide to Windows Installer XML by Nick Ramirez, the log and message methods don't work when a custom action is called from a UI control.

Answer 3

If you want a dialog to show up that contains the message, you must do it yourself.
Here's some code I use to do error handling in managed custom actions that run SQL.
It shows a messagebox if the installation is operating with a full UI.
It's in c# but hopefully you'll get the idea.
private void _handleSqlException(SqlException ex)
{
StringBuilder errorMessage = new StringBuilder();
errorMessage.Append("A SQL error has occurred.");
for (int i = 0; i < ex.Errors.Count; i++)
{
errorMessage.Append("Index #" + i + "\n" +
"Message: " + ex.Errors[i].Message + "\n" +
"LineNumber: " + ex.Errors[i].LineNumber + "\n" +
"Source: " + ex.Errors[i].Source + "\n" +
"Procedure: " + ex.Errors[i].Procedure + "\n");
}
session.Log(errorMessage);
if (session["UILevel"] == "5")
{
MessageBox.Show(errorMessage);
}
}