Daniel Cazzulino's Blog : Crazy Linq: replacing multiple and nested foreach statements with a query

Crazy Linq: replacing multiple and nested foreach statements with a query

Objective of the method: determine whether the given EnvDTE code class contains the given GeneratedCodeAttribute:

“old” foreach/if approach:

private bool IsPresentationModel(CodeClass2 baseClass)
{
    foreach (CodeClass2 pc in baseClass.PartialClasses)
    {
        foreach (CodeAttribute2 attr in pc.Attributes)
        {
            if (attr.FullName == typeof(GeneratedCodeAttribute).FullName &&
                attr.Value.Contains(ThisAssembly.Title))
            {
                return true;
            }
        }
    }

    foreach (CodeAttribute2 attr in baseClass.Attributes)
    {
        if (attr.FullName == typeof(GeneratedCodeAttribute).FullName &&
            attr.Value.Contains(ThisAssembly.Title))
        {
            return true;
        }
    }

    return false;
}

Note that most collections in the EnvDTE code model are not IEnumerable. Here's the linq-ified version:

private bool IsPresentationModel(CodeClass2 baseClass)
{
    return baseClass.PartialClasses
        .OfType<CodeClass2>()
        .Select(cc => cc.Attributes)
        .SelectMany(ce => ce.OfType<CodeAttribute2>())
        .Concat(baseClass.Attributes.OfType<CodeAttribute2>())
        .Where(attr =>
            attr.FullName == typeof(GeneratedCodeAttribute).FullName &&
            attr.Value.Contains(ThisAssembly.Title))
        .Any();
}

The SelectMany invocation is needed to flatten the list of attributes from all partial classes :)

Update: Changed Count() to Any() which is generally more optimal, as I only care about knowing whether there’s at least one such attribute, regardless of how many.

/kzu

/kzu dev↻d