TryParse

We want result to be set to the value of someObject.SomeProperty, and in any other case to default to 99.

int result =  0;
int max = int.TryParse(someObject.SomeProperty, out result) ? result : 99;

equivalent to

int result =  0;
int max = 99;

if(int.TryParse(someObject.SomeProperty, out result) == true) 
{
    max =  result; 
}
else // ok, maybe this 'else' is redundant
{ 
    max = 99;
}

Throw exception

When using throw after catching and handling an exception:

private void SaveRecord(Record record)
{
    try
    {
        var db = new NorthwindDB();
        db.SaveRecordInfo(null, record.ClientID, DateTime.Now).Execute(); // let's say this is the line 45
    }
    catch (Exception ex)
    {
        _logger.Error("Failed saving db record", ex);
        throw;
    }            
}

We will get something like the following:

System.Transactions.TransactionManagerCommunicationException: blah blah blah ...
at SampleApp.DataAccess.Repository.SaveRecord(Record record) in C:\Projects\SampleApp.DataAccess\Repository.cs:line 45

Which is what we want, in this example we want to log the exception and then re-throw it without losing the stack trace info (and the exact line of code where the exception occurred)

Subsonic ActiveRecord CreatedBy, ModifiedBy, etc

On ActiveRecord.tt

public void Update(IDataProvider provider){
...
}

removed the following block codes:

if(tbl.Columns.Any(x=>x.Name=="ModifiedBy")){
   if(String.IsNullOrEmpty(this.ModifiedBy))
       this.ModifiedBy=Environment.UserName;
}

if(tbl.Columns.Any(x=>x.Name=="ModifiedOn")){
    this.ModifiedOn=DateTime.Now;
}

after that the method should look like the one below:

public void Update(IDataProvider provider) {
    if(this._dirtyColumns.Count>0)
        _repo.Update(this,provider);
    OnSaved();
}

Similarly remove the rest of the Update() methods. Do the same with the Add() methods.