C# Refactoring Adventures in LINQ

I was presented with a scenario recently which I felt an ideal opportunity to begin my adventures into LINQ.

Essentially I had to parse a collection setting a property in objects within the collection based on a condition.

The requirement is more obvious when presented in its standard iterative solution:

//standard iteration
foreach (LogFileDataItem lfd in logFileData)
{
    if (lfd.FileName.Equals(currentLine, StringComparison.OrdinalIgnoreCase))
    {
        lfd.SQLScriptExecuted = true;
    }
}

Quite simple really.

So how would we express this in LINQ? Well, the following ought to suffice:

IEnumerable retrievedScripts;
retrievedScripts = from logFileDataItem in logFileData
                   where logFileDataItem.FileName.Equals(currentLine)
                   select logFileDataItem;

foreach (LogFileDataItem lfd in retrievedScripts)
{
    lfd.SQLScriptExecuted = true;
}

However, the above is more verbose than its predecessor, so we can refactor, removing the IEnumerable retrievedScripts variable:

foreach (LogFileDataItem lfd in
         from logFileDataItem in logFileData
         where logFileDataItem.FileName.Equals(currentLine)
         select logFileDataItem)
{
    lfd.SQLScriptExecuted = true;
}

Ahhh, but wait, aren’t Lambda Expressions even more concise? Well, yes, so here it is in Lambda Expressions:

//can be expressed in lambda expressions as:
foreach (LogFileDataItem lfd in logFileData.Where(item => item.FileName.Equals(currentLine)
                                           .Select(item => item))
{
    lfd.SQLScriptExecuted = true;
}

But which is best? Time to consult Stackoverflow?

Well, for starters, the .Select(item => item) is totally useless. So, happy days! More refactoring:

foreach (LogFileDataItem lfd in logFileData.Where(item => item.FileName.Equals(currentLine)))
{
    lfd.SQLScriptExecuted = true;
}

And John Skeet (no less!) recommends we actually move the where clause out. Who am I to argue?

IEnumerable lines = logFileData.Where(item => item.FileName.Equals(currentLine));
foreach (LogFileDataItem lfd in lines)
{
    lfd.SQLScriptExecuted = true;
}

And as for their relative differences? Well, not much as it would appear. It’s really just a matter of personal preference.