Question

With SubSonic 3 / ActiveRecord, is there an easy way to compare two records without having to compare each column by column. For example, I’d like a function that does something like this (without having to write a custom comparer for each table in my database):

public partial class MyTable
{
    public IList<SubSonic.Schema.IColumn> Compare(MyTable m)
    {
        IList<SubSonic.Schema.IColumn> columnsThatDontMatch = new...;
        if (this.Field1 != m.Field1)
        {
            columnsThatDontMatch.add(Field1_Column);
        }
        if (this.Field2 != m.Field2)
        {
            columnsThatDontMatch.add(Field2_Column);
        }
        ...
        return columnsThatDontMatch;
    }
}

In the end, what I really need is a function that tests for equality between two rows, excluding the primary key columns. The pseudo-code above is a more general form of this. I believe that once I get the columns that don’t match, I’ll be able to check if any of the columns are primary key fields.

I’ve looked through Columns property without finding anything that I can use. Ideally, the solution would be something I can toss in the t4 file and generate for all my tables in the database.

Answer 1

The best way, if using SQL Server as your backend as this can be auto populated, is to create a derived column that has a definition that uses CHECKSUM to hash the values of “selected” columns to form a uniqueness outside of the primary key.

EDIT: if you are not using SQL Server then this hashing will need to be done in code as you save, edit the row.