Dear all,

What is the recommended way to handle database constraints and display friendly user messages?

I am to show it, but here is how I handle fk constraints:

/// <summary>
/// Removes the quota.
/// </summary>
/// <param name="quotaId">The quota id.</param>
/// <returns>True if the quota was deleted.</returns>
internal bool RemoveQuota(long quotaId) {
  using (DataAccessAdapter adapter = new DataAccessAdapter()) {
    try {
      QuotaEntity quota = new QuotaEntity(quotaId);
      return adapter.DeleteEntity(quota);
    } catch (ORMException ex) {
      if (ex.Message.Contains("FK_ProjectQuota_Quota") || ex.Message.Contains("FK_ProjectHistoricalQuota_Quota")) {
        throw new Application.UserMessageException("Unable to delete this quota because it is in use by at least one project.");
      }
      throw new Application.UserMessageException(ex.Message);
    }
  }
}

Should I first do a query to check that the entity is not in use or is there another exception strategy I can use?

With kind regards,

Tore.

You can rely on the exception returned from the database, as the above code shows.

Ok, but you do not feel it is ugly hard coding the name of the fk constraint and relying on llblgen to include it in the exception message for future releases?

if you want a general exception message for a sql exception, just catch the SqlException and return "A problem occured".

if you want a detailed exception message for a specific problem i would recommend checking for the missing value before continuing.

A simple scalar query returning the count, or GetDbCount() would do the trick.